Title of Invention

A LUBRICATING OIL COMPOSITION

Abstract

The present invention relates to a lubricating oil composition comprises a mineral base oil selected from the group consisting of paraffinic and naphthenic lubricating base oils and/or a synthetic base oil selected from the group consisting of poly-a-olefins and hydrides thereof, isobutene oligomer and hydrides thereof, isoparaffin, alkylbenzenes, alkylnaphthalenes, diesters, copolymers of a-olefins and diesters, polyol esters, dialkyldiphenyl ethers, and polypheyl ether, (A) an organic molybdenum compound in an amount of from 0.003 to 0.1 percent by mass in terms of molybdenum, (B) a boron-containing succinimide and/or a boron-free succinimide in an amount of from 0.08 to 0.3 percent by mass in terms of nitrogen and in a mass ratio of the nitrogen content to the molybdenum content of Component(A) of 1.6 or greater, (C) alkaline earth metal detergent selected from the group consisting of alkaline earth metal sulfonates, alkaline earth metal phenates and alkaline earth metal salicylates In an amount of 0.01 to 0.16 percent by mass in terms of alkaline earth metal, (D) zinc dithiophosphate in an amount of 0.01 to 0.1 percent by mass in terms of zinc, and (E) at least one member selected from the group consisting of phosphoric esters, phosphorus esters, and salts thereof in an amount of 0.1 percent by mass or less in terms of phosphorus, , based on the total mass of the composition, and the sulfated ash content of the composition being 1 percent by mass or less, based on the total mass thereof.

Full Text

Field of the Invention This invention relates to a .lubricating ail compos ition- , particularly to lubricating oil compositions with an excellent fuel consumption efficiency exhibited under a wide range of temperature conditions from mid temperatures to high temperatures, and more particularly to those in addition to an excellent fuel efficiency, having excellent friction properties particularly suitable for use in four-cycle motorcycle engines. Description of the Prior Art From the viewpoints of the recent environmental protection and particularly measures for the reduction of the amount of exhausted C02, it becomes one of the important issues to provide automobiles with reduced fuel consumption. For reducing fuel consumption, it has been studied to reduce the weight of a car body, enhance the fuel combustion efficiency, reduce the friction between mechanical parts of an engine, develop and improve the driving mechanism of an automobile, and use low fuel consumption engine oils. For instance, with regard to the friction reduction measure, the development of rarefied gas engines and direct injection engines have been progressed together with an improvement in terms of materials of an engine such as an improvement in the valve mechanisms, a reduction in the number of the piston rings, and a reduction in the surface roughness of the sliding members. The improvement of fuel consumption efficiency has been attempted by not only reducing the friction between the materials of manual and automatic transmissions but also developing new technologies which can provide excellent driving force transmitting properties, such as automatic transmissions equipped with a slip lock-up clutch and metal belt- and toroidal-type continuously variable transmissions. Recently, a transmission oil has been demanded which has low fuel consumption properties owing to its lower viscosity and friction properties and appropriate friction properties providing an excellent power transmission performance for a wet clutch or a metal belt. A lubricating oil used in a four-cycle motorcycle engine in which a single crankcase accommodates not only the engine but also the transmission and the power transmission parts thereof is required to have capabilities both as an engine oil and a transmission oil. The lubricating oil is also demanded to have a low fuel consumption efficiency. The above-described engines and driving mechanism as well as the four-cycle motorcycle engines have been further reduced in size and weight and enhanced in power output. In connection with this, the heat load to the lubricating oil to be used in such engines and mechanisms becomes higher than before. Therefore, the low fuel consumption efficiency not only at mid temperatures of about 80°C but also at elevated temperatures tends to become important for the lubricating oil. Particularly, since comparing with automobile engines, four-cycle engines motorcycle have a wide and high engine revolutions under normal driving conditions, the engine oil temperature is increasingly variable from a low temperature to a high temperature, depending on the running conditions. Therefore, an engine oil has been demanded which has a low and stable fuel consumption efficiency between low and high temperatures. On the other hand, gasoline engine automobiles and particularly diesel engine automobiles or motorcycles tend to be equipped with an exhaust gas purifying system such as an EGR (exhaust gas recirculation) device, a ternary- or acid catalyst, and a particulate filter {DPF ) . For the purpose of maintaining the performances of these devices, it has been progressed to lower the sulfur content of gasolines or diesel fuel oils. In addition to this, from the same point of view mentioned above, a study has been started in which to lower the ash and phosphorus contents of the engine oils. Such attempts have been conducted by reducing the amount of metallic detergents or 2inc dithiophosphate to be added both as excellent oxidation and wear inhibitors or by not using this. However, this attempt possibly mars the capabilities of the engine oils. it thus is a very difficult problem to lower the ash and phosphorus contents . As an example of a low fuel consumption engine oil, Japanese Patent Laid-Open Publication No. 8-3 02 3 78 discloses an engine oil composition which comprises a specific lubricating base oil and specific additives such as an alkaline earth metal salicylate detergent and a molybdenum dithiocarbamate each in an specific amount. Japanese Patent Laid-Open Publication No. 2000-087070 discloses an engine oil composition for four-cycle motorcycles which comprises a specific base oil and specific additives such as a metallic detergent and a friction modifier so as to reduce the oil consumption and has an excellent low fuel consumption efficiency at an engine revolution of 3,000 to 13,000 rpm. However, in the case where such engine oils are used in a four-cycle motorcycle as they are, they cause the very constant clutch slippage which, therefore, could lessen the power transmitting performance of the clutch as well as deteriorate the smoothness upon gear-change and cause the friction materials to be heated and burned, wear, and break. From such possible defeats, it is a common knowledge for those skilled in the art that it is extremely difficult to provide an engine oil having both low fuel consumption properties and anti-slip properties in a wet clutch. Therefore, the use of such low fuel consumption engine oils is limited to a particular motorcycle in which a measure for clutch slippage is taken. A four-cycle motorcycle engine oil has been demanded which has a wide range of usage, excellent fuel consumption properties at from mid temperatures to high temperatures, and excellent friction properties in a wet clutch. It is known that the addition of an organic molybdenum compound to a transmission oil extremely deteriorates the static friction properties in a wet clutch. There exists no practical low fuel consumption lubricating oil composition containing an organic molybdenum, for a driving mechanism. For the purpose of developing a lubricating oil composition for an engine equipped with an exhaust gas purifying device, the present inventors studied the low fuel consumption efficiency and friction properties in a wet clutch of a conventional low fuel consumption engine oil containing an organic molybdenum and an alkaline earth metal salicylate as disclosed used in examples of the above-mentioned publications for situations where it is decreased in the amount of the salicylate so as to lower the ash. As a result, it was found that the mid and high temperature friction properties which are regarded as important due to the recent increased heat load are deteriorated, leading to the deterioration of the fuel consumption efficiency and the friction properties in a wet clutch are also extremely deteriorated. It was also found that the low fuel consumption efficiency at high temperatures of the above-mentioned conventional engine oils were not satisfactory. Further, the present inventors discovered a four-cycle motorcycle engine oil composition having both low fuel consumption properties and anti-slip properties in a wet clutch and grading MA Class indicating no clutch slippage among the performance classification in accordance with JASO T 903-98 and had already filed a patent application for the engine oil composition (see Japanese Patent Application No-2000-028919 specification). However, it was also found that the composition still can be improved in static friction properties which are an index of acceleration response upon starting or after gear-change. Furthermore, it was also found that further study can be done for providing a low-ash type (low sulfated ash content type) composition which is reduced in the metallic detergent content and a low ash and phosphorus type composition which is reduced in the amount of zinc dithiophosphate. BREIF SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a low fuel consumption type lubricating oil composition containing an organic molybdenum compound which has excellent fuel consumption properties over the range of mid temperatures and high temperatures resulting from increased heat load even in the case of reducing the amount of the metallic detergent. Another object of the present invention is also to provide a low fuel consumption type lubricating oil composition containing an organic molybdenum compound whose sulfated ash content and phosphorus content are suppressed and which is suitably used for vehicles equipped with the above-described exhaust gas purifying device. Another object of the present invention is to provide a low fuel consumption type lubricating oil composition containing an organic molybdenum compound, which has excellent fuel consumption properties at from mid to high temperatures and is improved in static friction properties, i.e., an index of acceleration response upon starting and after gear-change. Further another object of the present invention is to provide a low fuel consumption type lubricating oil composition containing an organic molybdenum compound, which is improved in fuel consumption efficiency at from mid to high temperatures and in friction properties in a wet clutch so as to grade MA indicating no clutch slippage, among the performance classification defined by JASO T 903-98. Still another object of the present invention is to provide a lubricating oil composition suitable for a four-cycle motorcycle engine, which is improved in friction properties in a wet clutch so as to be equivalent to those of a four-cycle motorcycle engine oil which is free of an organic molybdenum compound and thus has no low fuel consumption properties, and has excellent fuel consumption properties at from mid to high temperatures . As a result of an extensive research and study, it was found that the above-mentioned problems can be solved by blending a lubricating base oil with (A) an organic molybdenum compound, (B) a succinimide ashless dispersant, (C) an alkaline earth metal detergent, (D) a zinc dithiophosphate, and (E) a phosphoric ester anti-wear agent each in a specific amount and at a specific ratio. According to the present invention, there is provided a lubricating oil composition comprises mineral and/or synthetic base oils, (A) an organic molybdenum compound in an amount of from 0.003 to 0.1 percent by mass in terms of molybdenum, {B) a boron-containing succinimide and/or a boron-free succinimide in an amount of from 0.08 to 0.3 percent by mass in terms of nitrogen and in a mass ratio of the nitrogen content to the molybdenum content of Component (A) of 1.6 or greater, (C) an alkaline earth metal detergent in an amount of 0.01 to 0.16 percent by mass in terms of alkaline earth metal, {D) zinc dithiophosphate in an amount of 0.01 to 0.1 percent by mass in terms of zinc, and (E) at least one member selected from the group consisting of phosphoric esters, phosphorus esters, and salts thereof in an amount of 0.1 percent by mass or less in terms of phosphorus, based on the total mass of the composition, and the sulfated ash content of the composition being 1 percent by mass or less, based on the total mass thereof. In the present invention, Component (A) is preferably a molybdenum dithiocarbamate. In the present invention, Component (B) comprises preferably a boron-containing succinimide and/or a boron-free mono and/or bis succinimide and the amount of the boron-containing succinimide is preferably from 0.005 to 0.2 percent by mass in terms of boron, based on the total mass of the composition. In the present invention, the amount of Component (C) is preferably from 0.01 to 0.07 percent by mass in terms of alkaline earth metal, based on the total mass of the composition. In the present invention, the amount of Component (D) is preferably from 0.01 to 0.06 percent by mass in terms of zinc, based on the total mass of the composition. In the present invention, the sulfated ash content in the composition is preferably 0.7 percent by mass or less, based on the total mass of the composition. In the present invention, the phosphorus content in the composition is preferably 0.08 percent by mass or less, based on the total mass of the composition. The lubricating oil composition of the present invention is preferably used as an engine oil for an automobile equipped with an exhaust gas purifying device. The lubricating oil composition of the present invention is preferably used as an engine oil for a four-cycle motorcycle. DETAILED DESCRIPTION OF THE INVENTION The lubricating oil with improved friction properties of the present invention will be described below. The lubricating base oil for the lubricating oil composition of the present invention may be any type of base oil as long as it can be used as a base oil for a normal engine oil composition and thus may be any mineral- or synthetic- base oil. Examples of the mineral base oil are paraffinic and naphthenic lubricating base oils which can be obtained by subjecting a lubricating oil fraction produced by atmospheric- or vacuum- distilling a crude oil, to two or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxinq, catalytic dewaxing, hydrorefining, washing with sulfuric acid, and clay treatment. Examples of the synthetic base oil are poly-a -olefins such as polybutene, 1-octene oligomer, 1-decene oligomer, and ethylene-propylene oligomer, and hydrides thereof, isobutene oligomer and hydrides thereof, isoparaffin, alkylbenzene, alkylnaphthalene, diesters such as dibutyl malate, ditridecyl glutarate, and di-2-ethylhexyl sebacate, copolymers of a-olefins and diesters, polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethyl hexanoate, and pentaerythritol pelargonate, dialkyldiphenyl ether, and polyphenyl ether. The lubricating base oil to be used in the present invention may be one of the above-exemplified mineral or synthetic oils, a mixture of the two or more mineral oils or the two or more synthetic oils, or a mixture of the mineral oil and the synthetic oil. The mixing ratio of the two or more base oils can be selected arbitrary. Although no particular limitation is imposed on the amount of aromatics of the base oil, it is preferably 15 percent by mass or less, more preferably 10 percent by mass or less, and further more preferably 5 percent by mass or less and 2 percent by mass or greater. The term "the amount of aromatics" denotes the amount of aromatics fraction determined in accordance with ASTM D2549. No particular limitation is imposed on the viscosity of the base oil. However, the lower limit of the kinematic viscosity at 100°C is preferably 2 mmVs and more preferably 3 mm2/s, while the upper limit is preferably 10 mmVs and more preferably 8 mmVs. The use of a base oil with a kinematic viscosity at 100°C of 2 mmVs or greater is contributive to the production of a lubricating oil composition which is excellent in lubricity due to its sufficient oil film formation capability and less in evaporation loss of the base oil under high temperature conditions, i.e., excellent in fuel consumption properties. Whereas, the use of a base oil with a kinematic base oil at 100°C of 10 mmVs or less makes it possible to produce a lubricating oil composition which is less in flow resistance and thus in friction resistance at the site of lubrication, leading to excellent fuel consumption properties. Although no particular limitation is imposed on the viscosity index of the base oil to be used in the present invention, it is preferably 80 or greater and more preferably 100 or greater. The lubricating oil 1 -!• composition contains a base oil with a viscosity index of 120 or greater in an amount of 15 percent by mass or more. The base oil has particularly preferably a viscosity index of 120 or greater. The use of a base oil with a viscosity index of 80 or greater makes it possible to produce a lubricating oil composition which is excellent in less fuel consumption properties and less in evaporation loss of the base oil under high temperature conditions . The NOACK volatility of the base oil to be used in the present invention is preferably 20 percent by mass or less, more preferably 16 percent by mass or less, and particularly preferably 10 percent by mass or less. The use of a base oil with a NOACK volatility of 20 percent by mass or less makes it possible to produce a lubricating oil composition which is less in evaporation loss under high temperature conditions and can avoid adversely affecting, due to the accumulation in the exhaust gas purifying device, on the pistons and in the combustion chamber. The term "NOACK volatility" used herein denotes the amount of volatility when 60 g of a sample oil is evaporated under the conditions of 250°C and -20mmH2O for one hour, in accordance with CEC L-40-T-87. Component (A) of the lubricating oil composition of the present invention is an organic molybdenum compound. Component (B) is a boron-containing succinimide and/or a boron-free succinimide. Component (C) is an alkaline earth metal detergent. Component (D) is zinc dithiophosphate. Component (E) is phosphoric esters, phosphorus esters, and salts thereof hereinafter referred to as phosphate or phosphite compounds . Examples of Component (A) are molybdenum dithiocarbamates and molybdenum dithiophosphates. Specific examples of the molybdenum dithiocarbamates are those represented by formula (1) below and specific examples of the molybdenum dithiophosphates are those represented by formula (2) below: wherein Rl, R1, R3, and R4 are each independently a hydrocarbon group having 1 to 24 carbon atoms, a is an integer of 0 to 4, b is an integer of 0 to 4, and a + b = 4 ; and wherein R5, R6, RT and R* are each independently a hydrocarbon group having 1 to 24 carbon atoms, c is an integer of 0 to 4, d is an integer of 0 to 4, and c + d = 4. Preferred examples of the hydrocarbon groups for Rl, R2, R!, and Ra in formula (1) and R5, R6, R7 and R6 in formula (2) are straight-chain or branched alkyl groups having 1 to 24 carbon atoms, cycloalkyl or straight-chain or branched alkylcycloalkyl groups having 5 to 13 carbon atoms, straight-chain or branched alkenyl groups having 3 to 24 carbon atoms, aryl or straight-chain or branched alkylaryl groups having 6 to 18 carbon atoms, and arylalkyl groups having 7 to 19 carbon atoms. The alkyl and alkenyl groups may be of primary, secondary or tertiary. Specific examples of the alkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, and tetracosyl groups, which may be straight-chain or branched. Specific examples of the cycloalkyl groups and alkylcycloalkyl groups are cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups and alkylcycloalkyl groups such as methylcyclopentyl, dimethylcyclopentyl, ethylcyclopentyl, propylcyclopentyl, ethylmethylcyclopentyl, trimethylcyclopentyl, diethylcyclopentyl, ethyldimethylcyclopentyl, propylmethylcyclopentyl, propylethylcyclopentyl, dipropylcycLopentyl, propylethylmethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, ethylcyclohexyl, propylcyclohexyl, ethylmethylcyclohexyl, trimethylcyclohexyl, diethylcyclohexyl, ethyldimethylcyclohexyl, propylmethylcyclohexyl, propylethylcyclohexyl, dipropylcyclohexyl, propylethylmethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, ethylcycloheptyl, propylcycloheptyl, ethylmethylcycloheptyl, trimethylcycloheptyl, diethylcycloheptyl, ethyldimethylcycloheptyl, propylmethylcycloheptyl, propylethylcycloheptyl, dipropylcycloheptyl, and propylethylmethylcyclohepty1 groups, of which alkyl groups may be straight-chain or branched and may bonded to any position of the cycloalkyl groups. Specific examples of the alkenyl groups are propenyl, isopropenyl, butenyl, butandienyl, pentenyl, hexenyl, heptenyl, octenyl, noneyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadeceny1, hexadecenyl, heptadecenyl, octadecenyl such as oleyl, nonadecenyl, eicosenyl, heneicosenyl, dococenyl, tricosenyl, and tetracosenyl groups, all of which may be straight-chain or branched and the position of which double bond may vary. Specific examples of the aryl and alkylaryl groups are aryl groups such as phenyl and naphtyl groups and alkylaryl groups such as tolyl, xylyl, ethylphenyl, propylphenyl, ethylmethylphenyl, trimethylphenyl, butylphenyl, propylmethylphenyl, diethylphenyl, ethyldimethylphenyl, tetramethylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, of which alkyl groups may be straight-chain or branched and may bond to any position of the aryl groups. Specific examples of the arylalkyl groups are benzyl, methylbenzyl, dimethylbenzyl, phenetyl, methylphenetyl, and dimethylphenetyl, of which alkyl groups may be straight-chain or branched and may bond to any position of the aryl groups. Particularly preferred examples of each R1, R3, R3, R4, R5, Rs, R7 and R9 are a straight-chain or branched alkyl group having 1 to 18 carbon atoms or an aryl or straight-chain or branched alkylaryl group having 6 to 18 carbon atoms. Preferred molybdenum dithiocarbamates for Component (A) used in the present invention are molybdenum dialkyldithiocarbamate of formula (1) wherein R1, R:, R3, and R4 are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, or tridecyl, all of which may be straight-chain or branched, a = 4, and b = 0; sulfurized molybdenum dialkyldithiocarbamate of formula (1) wherein R1, R2, R3, and R" are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, or tridecyl, all of which may be straight-chain or branched, a = 0, and b = 4 ; sulfurized oxyraolybdenum dialkyIdithiocarbamate of formula (1) wherein R1, R2, R3, and R4 are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, or tridecyl, all of which may be straight-chain or branched, a = 1 to 3, b = 1 to 3, and a + b = 4; and a mixture of two or more compounds selected from the group consisting of the molybdenum dialkyIdithiocarbamate, sulfurized molybdenum dialkyldithiocarbamate, and sulfurized oxymolybdenum dialkyIdithiocarbamate mixed at an arbitrary ratio. These compounds may be those having in one molecule alkyl groups with different carbon number and structure from each other. Specific examples of particularly preferred molybdenum dithiophosphate of formula (2) are molybdenum dialkyldithiophosphates of formula (2) wherein R5, R6, R7, and R8 are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl groups, all of which may be straight-chain or branched, c = 4, and d = 0; sulfurized molybdenum dialkyldithiophosphates of formula (2) wherein R5, R6, RT, and RB are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl groups, all of which may be straight-chain or branched, c = 0, and d = 4; sulfurized oxymolybdenum dialkyldithiophosphates of formula (2) wherein R5, R°, R7, and R8 are each independently butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and tridecyl groups, all of which may be straight-chain or branched, c = 1 to 3 , d = 1 to 3, and c + d = 4; and a mixture of two or more compounds selected from the group consisting of the molybdenum dialkyldithiophosphates, sulfurized molybdenum dialkyldithiophosphates, and sulfurized oxymolybdenum dialkyldithiophosphates mixed at a suitable ratio. These compounds may be those having in one molecule alkyl groups with different carbon number and structure from each other. Other than the above-exemplified compounds, the organic molybdenum compound used in the present invention is also exemplified by organic molybdenum complexes which are the reaction products of basic nitrogen-containing compounds such as succinimides, acid molybdenum compounds such as molybdenum trioxide, and sulfur compounds such as hydrogen sulfide and phosphorus pentasulf ide. In the lubricating oil composition of the present invention, the lower limit content of Component (A) is 0.003 percent by mass and preferably 0.01 percent by mass in terms of molybdenum, based on the total mass of the composition. The upper limit content of Component (A) is 0.1 percent by mass, preferably 0.08 percent by mass, and particularly preferably 0.0 6 percent by mass in terms of molybdenum, based on the total mass of the composition. Component (A) of less than the lower limit would fail to attain sufficient fuel consumption efficiency, while Component (A) exceeding the upper limit would fail to improve fuel consumption efficiency balancing the amount and deteriorate the friction properties in a wet clutch. Preferred Components (A) to be used in the present invention are molybdenum dithiophosphates and molybdenum dithiocarbamates. However, particularly preferred are molybdenum dithiophosphates because they can improve the low fuel consumption efficiency at from mid temperatures and high temperatures and significantly improve the friction properties in a wet clutch synergistically with the other components. Component (B) is a boron-containing succinimide and/or a boron-free succinimide. Examples of the boron-free succinimide are monosuccinimides represented by formula {3} below, bissuccinimides represented by formula (4) below, and those modified with oxygen-containing organic compounds: In formulae (3) and (4), R10, R11, and R12 are each independently a polybutenyl group and n is an integer of 2 to 7. The polybutenyl group of R1Q, R11, and R12 has a number-average molecular weight of preferably 700 or greater and more preferably 900 or greater and preferably 3,500 or less and more preferably 1,500 or less. A polybutenyl group having a number-average molecular weight of 700 or greater makes it possible to produce a lubricating oil composition with excellent detergent and dispersion properties. Whereas, a polybutenyl group having a number-average molecular weight of 3,500 or less makes it possible to produce a lubricating oil composition with more excellent low-temperature flowability. From the view point of the effect of suppressing sludge formation, the lower limit of n is 2 and preferably 3, while the upper limit of n is 7 and preferably 6. The polybutenyl group can be obtained from polybutene {polyisobutene) produced by polymerizing a mixture of 1-buten and isobutene or a highly purified isobutylene using a catalyst such as aluminum chloride or boron fluoride. In the polybutene mixture, generally 5 to 100 percent by mol of those having a vinylidene structure at the terminal ends exist. The polybutene {polyisobutene) may be those of which a slight amount of the remaining fluorine and chlorine resulting from the catalyst used in the process has been removed with a suitable treatment. Therefore, the content of halogen atoms such as fluorine and chlorine is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less, further more preferably 5 ppm by mass or less, and particularly preferably 1 ppm or less. No particular limitation is imposed on the method of producing the succinimide represented by formula (3) or (4). For example, the succinimide may be produced by reacting a polybutenyl succinimide produced by reacting polybutene obtained by chlorinating the above polybutene, preferably one from which chorine and fluorine has been removed, with maleic anhydride at a temperature of 100 to 200 °C, with polyamine such as diethylene triamine, triethylene tetramine, tetraethylene pentamine or pentaethylene hexamine. In the case of producing the bissuccinimide, the polybutenyl succinimide in an amount (mol ratio) of twice as much as polyamine may be reacted therewith. In the case of producing the monosuccinimide, the polybutenyl succinimide in the same amount of that of polyamine may be reacted therewith. The boron-free succinimide may be a compound obtained by neutralizing or amidizing part or all of the remaining amino groups and/or imide groups by bringing a compound of formula (3) or (4) into a reaction with an oxygen-containing organic compound. Specific examples of the oxygen-containing organic compound are monocarboxylic acids having 1 to 30 carbon atoms, such as formic acid, acetic acid, glycolic acid, lactic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, oleic acid, nonadecanoic acid, and eicosanoic acid; polycarboxylic acid having 2 to 30 carbon atoms, such as oxalic acid, phthalic acid, trimellitic acid, andpyromelliticacid, and anhydrides thereof and ester compounds thereof, alkyleneoxides having 2 to 6 carbon atoms, and hydroxy(poly)oxyalkylene carbonates. By the reaction with such oxygen-containing organic compounds, part or whole of the amino or imino group in the compound of formula (3) or (4) assumedly has a structure as represented by formula (5) wherein Rl! is hydrogen, an alkyl, alkenyl or alkoxy group having 1 to 24 carbon atoms, or a hydroxy(poly)oxyalkylene group represented by -0-(R140)MH wherein R14 is an alkylene group having 1 to 4 carbon atoms and m is an integer of 1 to 5. The boron-containing succinimides are those obtained by reacting a compound of formula (3) or (4) with a boric compound. Examples of the boric compound are boric acid, borates, and boric acid esters. Specific examples of boric acid are orthoboric acid, methaboric acid, and tetraboric acid. Examples of borates are alkali metal salts, alkaline earth metal salts, or ammonium salts of boric acid. More specific examples are lithium borate such as lithium methaborate, lithium tetraborate, lithium pentaborate, and lithium perborate, sodium borate such as sodium methaborate, sodium diborate, sodium tetraborate, sodium pentaborate, sodium hexaborate, and sodium octoborate, potassium methaborate, potassium tetraborate, potassium pentaborate, potassium hexaborate, and potassium octoborate, calcium borate such as calcium methaborate, calcium diborate, tricalcium tetraborate, pentacalcium tetraborate, and calcium hexaborate, magnesium borate such as magnesium methaborate, magnesium diborate, trimagnesium tetraborate, pentamagnesium tetraborate, and magnesium hexaborate, and ammonium borate such as ammonium methaborate, ammonium tetraborate, ammonium pentaborate, and ammonium octoborate. Examples of the boric acid esters are esters of boric acid and an aliphatic alcohol having 1 to 6 carbon atoms and more specifically monomethyl borate, dimethyl borate, trimethyl borate, monoethyl borate, diethyl borate, triethyl borate, monopropyl borate, dipropyl borate, tripropyl borate, monobutyl borate, dibutyl borate, and tributyl borate. No particular limitation is imposed on the mass ratio of boron and nitrogen (B/N ratio) in the boron-containing succinimide to be used in the present invention. However, the lower limit of the ratio is 0.2, preferably 0.3, and more preferably 0.5 while the upper limit is 1.2, preferably 1, and more preferably 0.9. The ratio of less than the lower limit results in a lubricating oil composition which is less effective, while the ratio exceeding the upper limit would cause poor oxidation stability. Although the above-described boron-containing succinimide and boron-free mono- or bis-succinimide may be used alone, respectively as Component {B}, it is preferred to use the boron-containing succinimide alone or in combination with the boron-free mono- or bis-succinimide because further improvement in friction properties in a wet clutch can be expected. The mix ratio (mass ratio) of the above-described boron-containing succinimide to the boron-free succinimide is preferably from 100 : 0 to 20 : 80, more preferably from 90 : 10 to 40 : 60, and particularly preferably from 70 : 30 to 45 : 55. The lower limit content of Component (B) is 0.08 percent by mass and preferably 0.09 percent by mass in terms of nitrogen, based on the total mass of the composition of the present invention. The upper limit content of Component (B) is 0.3 percent by mass and preferably 0.2 percent by mass in terms of nitrogen, based on the composition of the present invention. The use of Component (B) of less than the lower limit content results in a lubricating oil composition which is not sufficiently improved in fuel consumption efficiency at from mid to high temperatures and friction properties in a wet clutch. The use of Component (B) exceeding the upper limit content deteriorates the fuel consumption efficiency, low-temperature viscosity and anti-emulsion properties of the resulting lubricating oil composition. For the same reasons, the lower limit content of the boron-containing succinimide is 0.005 percent by mass, preferably 0.01 percent by mass, and more preferably 0.02 percent by mass in terms of boron, based on the total mass of the composition, while the upper limit is 0.2 percent by mass, preferably 0.1 percent by mass, more preferably 0.08 percent by mass, and particularly preferably 0.0 5 percent by mass in terms of boron, based on the total mass of the composition. The boron-containing succinimide exceeding the upper limit would adversely affect the exhaust gas purifying device. In the lubricating oil composition of the present invention, the lower limit of the mass ratio Component (B) in terms of nitrogen to Component {A} in terms of molybdenum is 1.6, preferably 1.8, and particularly preferably 2.1, while the upper limit of the mass ratio is 100, preferably 10, more preferably 5, and particularly preferably 4. The mass ratio of less than the lower limit would result in a lubricating oil composition with poor fuel consumption efficiency at from mid to high temperatures and friction properties in a wet clutch, while the mass ratio exceeding the upper limit would fail to provide sufficient fuel consumption efficiency. Next, an alkaline earth metal detergent, i.e., Component (C) is described in detail. Component (C) may be alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. In the present invention, eligible alkaline earth metal detergents are one or more members selected from these compounds. Preferred alkaline earth metal sulfonates are alkaline earth metal salts, preferably magnesium salts and/or calcium salts, and particularly preferably calcium salts, of alkyl aromatic sulfonic acids obtained by sulfonating an alkyl aromatic compound having a molecular weight of 300 to 1,500 and preferably 400 to 700. Specific examples of the alkyl aromatic sulfonic acid are petroleum sulfonic acids and synthetic sulfonic acids . The petroleum sulfonic acid may be mahogany acid obtained by sulfonating the alkyl aromatic compound contained in the lubricant fraction of a mineral oil or by-produced upon production of white oil. The synthetic sulfonic acid may be those obtained by sulfonating an alkyl benzene having a straight-chain or branched alkyl group, which may be by-produced from a plant for producing an alkyl benzene used as materials of detergents or obtained by alkylating an oligomer of an olefin having 1 to 12 carbon atoms such as ethylene and propylene to benzene or sulfonating dinonylnaphthalene. Although not restricted, there may be used fuming sulfuric acid and sulfuric anhydride as a sulfonating agent- In the present invention, the petroleum based alkaline earth metal sulfonates have effects of improving the fuel consumption efficiency at from mid to high temperatures and static friction properties in a wet clutch, while the synthetic ones have effects of improving particularly the fuel consumption efficiency at high temperatures and stop time index. Therefore, they can be selected depending on the necessity. Examples of the alkaline earth metal phenates are alkaline earth metal salts, particularly magnesium salts and calcium salts of alkylphenols, alkylphenolsulfides or the Mannich reaction products of alkylphenols. Specific examples are those represented by formulae (6) through (8): In formulae (6), (7), and (8), R21, R22, R23, R24, R25, and R2S may be the same or different and are each independently a straight-chain or branched alkyl group having 4 to 30, preferably 6 to 18 carbon atoms, M1, M2, and H1 are each independently an alkaline earth metal, preferably calcium and magnesium, and x is an integer of 1 or 2. Specific examples of the alkyl group for R21, R2i, R2!, R24, R;5, and R2° are butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecy1, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, and triacontyl groups. These alkyl groups may be straight-chain or branched and may be of primary, secondary, or tertiary. In the present invention, the alkaline earth metal phenates are preferably used because they can improve the fuel consumption efficiency at from mid to high temperatures and the friction properties in a wet clutch. Examples of the alkaline earth metal salicylates are alkaline earth metal salts, preferably magnesium and calcium salts of an alkyl salicylic acid. Specific examples are compounds represented by formula (9) In formula (9), R27 is a straight-chain or branched alkyl group having 4 to 30, preferably 6 to 18 carbon atoms and M4 is an alkaline earth metal, preferably calcium or magnesium. Specific examples of the alkyl group for R27 are butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, docosyl, tricosyl, tetracosyl, pentacosyl, hexacosyl, heptacosyl, octacosyl, nonacosyl, and triacontyl groups. These alkyl groups may be straight-chain or branched and may be of primary, binary or tertiary. In the present invention, these alkaline earth metal salicylates are preferably used because they can improve the fuel consumption efficiency and friction properties in a wet clutch. Component (C) may be neutral alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates obtained by reacting alkylaromatic sulfonic acids, alkylphenols, alkylphenolsuflides, the Mannich reaction products of alkylphenolsulfides or alkyl salicylic acid directly with an alkaline earth metal base of the oxide or hydroxide of an alkaline earth metal such as magnesium and/or calcium or substituting alkylaromatic sulfonic acids, alkylphenols, alkylphenolsuflides, the Mannich reaction products of alkylphenolsulfides or alkyl salicylic acid which has been converted to an alkali metal salt such as sodium salt and potassium salt, with an alkaline earth metal salt. Alternatively, Component (C) may be basic alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates obtained by heating the neutral alkaline earth metal sulfonates, alkaline earth metal phenates or alkaline earth metal salicylates with an excess amount of an alkaline earth metal salt or alkaline earth metal base in the presence of water. Further alternatively, Component {C) may be overbased alkaline earth metal sulfonates, alkaline earth metal phenates and alkaline earth metal salicylates obtained by reacting the hydroxide of an alkaline earth metal with carbonic acid gas or boric acid in the presence of the neutral alkaline earth metal sulfonates, alkaline earth metal phenates or alkaline earth metal salicylates. In the present invention, there may be used the above-described alkali metal salts, neutral alkaline earth metal salts, basic alkaline earth metal salts, overbased alkaline earth metal salts, and mixtures thereof. Commercially available metallic detergents are usually diluted with a light lubricating base oil. It is preferred to use metal-based detergents of which metal content is within the range of 1.0 to 20 percent by mass, preferably 2.0 to 16 percent by mass. No particular limitation is imposed on the total base number of Component (C). However, in order to obtain an excellent detergency, Component (C) has a total base number of 500 mgKOH/g or less, preferably 150 to 450 mgKOH/g. The term "total base number" used herein, denotes a total base number measured by the perchloric acid potentiometric titration method in accordance with section 7 of JIS K2501 (1992) "Petroleum products and lubricants-Determination of neutralization number". The lower limit content of Component { C ) in the lubricating oil composition of the present invention is 0.01 percent by mass, preferably 0.02 percent by mass, and more preferably 0.04 percent by mass. The upper limit content of Component (C) is 0.16 percent by mass which successfully lowers ash formation, but preferably 0.13 percent by mass and more preferably 0.07 percent by mass. Component (C) of less than the lower limit content deteriorates the fuel consumption efficiency at from mid to high temperatures and friction properties for a wet clutch, while Component (C) exceeding the upper limit can improve the friction properties for a wet clutch but fails to make the resulting lubricating oil with lower ash formation properties, leading to the accumulation of ash in the exhaust gas purifying device or combustion chamber. Specific examples of Component (D), i.e., zinc dithiophosphate are compounds represented by formula In formula (10), R11, Ri2 , R!i, and R34 are each independently a hydrocarbon group having 1 to 24 carbon atoms. The hydrocarbon groups having 1 to 24 carbon atoms for R31, R32, R33, and R3* are the same as those described with respect to R1, R2, R3, and R4 in formula {1) above. Preferred compounds represented by formula (10) are zinc dialkyldithiophosphate of which alkyl group may be straight-chain or branched, such as zinc dimethyldithiophosphate, zinc diethyldithiophosphate, zinc dipropyIdithiophosphate, zinc dibutyldithiophosphate, zinc dipentyldithiophosphate, zinc dihexyldithiophosphate, zinc diheptyldithiophosphate, zinc dioctyldithiophosphate, zinc dinonyldithiophosphate, zinc didecyldithiophosphate, zinc diundecyIdithiophosphate, zinc didodecyldithiophosphate, zinc ditridecyldithiophosphate, zinc ditetradecyldithiophosphate, zinc dipentadecyldithiophosphate, zinc dihexadecyldithiophosphate, zinc diheptadecyldithiophosphate, and zinc dioctadecyldithiophosphate; zinc dipehnyldithiophosphate; zinc dialkyIphenyIdithiophosphate wherein the alkyl group may be straight-chain or branched and may bond to any position of the phenyl group, such as zinc ditolyldithiophosphate, zinc dixylyldithiophosphate, zinc diethylphenyldithiophosphate, zinc dipropylphenyldithiophosphate, zinc dibutylphenyldithiophosphate, zinc dipentylphenyldithiophosphate, zinc dihexylphenyldithiophosphate, zinc diheptylphenyldithiophosphate, zinc dioctylphenyldithiophosphate, zinc dinonylphenyldithiophosphate, zinc didecylphenyldithiophosphate, zinc diundecylphenyldithiophosphate, and zinc didodecylphenyldithiophosphate; and a mixture of two or more of these compounds mixed at a suitable ratio. These zinc dialkyldithiophosphates and zinc dialkylphenyldithiophosphates may have alkyl groups having different carbon number and structure from each other in one molecule. In the present invention. Component { D ) is preferably a mixture of zinc dithiophosphate having a primary alkyl group (primary ZDTP ) and zinc dithiophosphate having a secondary alkyl group {secondary ZDTP). The mixing ratio {mass ratio) of a primary ZDTP to a secondary ZDTP is preferably from 5 : 95 to 50 : 50 and more preferably from 10 : 90 to 40 : 60. The mixing ratio of these ranges results in a lubricating oil composition which can obtain the effect intended by the invention and is excellent anti-wear properties. The upper limit content of Composition (D) in the lubricating oil composition of the present invention is 0.1 percent by mass, preferably 0.08 percent by mass, and more preferably 0.06 percent by mass in terms of zinc, based on the total mass of the composition. The lower limit content of Composition {D) is 0.01 percent by mass and preferably 0.02 percent by mass in terms of zinc, based on the total mass of the composition. Component (D) exceeding the upper limit content would adversely affect the exhaust gas purifying device due to the phosphorus or zinc and be poor in fuel consumption efficiency at high temperatures and friction properties in a wet clutch. Component (D) of less than the lower limit content would result in a lubricating oil composition which is poor in anti-wear properties and fuel consumption efficiency due to the reduced amount of molybdenum disulfide at the slipping parts caused by the decrease of sulfur source of the composition. The content of Composition (D) in the above-specified range makes it possible to produce a lubricating oil composition which is excellent in fuel consumption efficiency at from low to high temperatures and particularly improved in friction properties in a wet clutch. Component (E), i.e., a phosphorus or phosphoric ester compound is described. Examples of Component (E) are phosphoric monoesters, phosphoric diesters, phosphoric triesters, phosphorus monoesters, phosphorus diesters, phosphorus triesters, thiophosphoric esters, dithiophosphoric esters, trithiophosphoric esters, thiophosphorus esters, dithiophosphorus esters, trithiophosphorus esters, and salts thereof. These compounds each have preferably a hydrocarbon group having 3 to 20 carbon atoms. Examples of the hydrocarbon group having 3 to 20 carbon atoms are alkyl, cycloalkyl, alkenyl, aryl, and arylalkyl groups, which may have a substituent. Examples of the alkyl group are ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups, which may be straight-chain or branched- Examples of the cycloalkyl group are those having 5 to 7 carbon atoms, such as cyclopentyl, cyclohexyl, and cycloheptyl groups. Examples of the alkyl-substituted cycloalkyl group are those having 6 to 11 carbon atoms such as methylcyclopenty1, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl. methylethylcycloheptyl, and diethylcycloheptyl groups, wherein the position of the alkyl group may vary. Examples of the alkenyl group are butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, and octadecenyl groups, which may be straight-chain or branched and the position of which double bond may vary. Examples of the aryl group are phenyl and naphtyl groups. Examples of the alkyl-substituted aryl group are those having 7 to 18 carbon atoms, such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylpheny1, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl groups, wherein the alkyl group may be straight-chain or branched and the position thereof to the aryl group may vary. Examples of the arylalkyl group are those having 7 to 12 carbon atoms, such as benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl, and phenylhexyl groups, wherein the alkyl group may be straight-chain or branched. Examples of preferred compounds for Component (E) are monoalkyl phosphates such as monopropyl phosphate, monobutyl phosphate, monopentyl phosphate, monohexyl phosphate, monoheptyl phosphate, and monooctyl phosphate, wherein the alkyl groups may be straight-chain or branched; mono(alkyl)aryl phosphates such as monophenyl phophate and monocresyl phosphate; di(alkyl}aryl phosphates such as dipropyl phosphate, dibutyl phosphate, dipentyl phosphate, dihexyl phosphate, diheptyl phosphate, and dioctyl phosphate wherein the alkyl groups may be straight-chain or branched; di(alkyl)aryl phosphates such as diphenyl phosphate and dicresyl phosphate; trialkyl phosphates such as tripropyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, and trioctyl phosphate, wherein the alkyl groups may be straight-chain or branched; tri(alkyl)aryl phosphates such as triphenyl phosphate and tricresyl phosphate; monoalkyl phosphites such as monoproyl phosphite, monobutyl phosphite, monopentyl phosphite, monohexylphosphite, monoheptylphosphite, and monooctyl phosphite, wherein the alkyl groups may be straight-chain or branched; mono(alkyl)aryl phophites such as monophenyl phosphite and monocresyl phosphite; dialkyl phosphites such as dipropyl phosphite, dibutyl phosphite, dipentyl phosphite, dihexyl phosphite, diheptyl phosphite, and dioctyl phosphite, wherein the alkyl groups may be straight-chain or branched; di(alkyl)aryl phosphites such as diphenyl phosphite and dicresyl phosphite; trialkyl phosphites such as tripropyl phosphite, tributyl phosphite, tripentyl phosphite, trihexyl phosphite, triheptyl phosphite, and trioctyl phosphite, wherein the alkyl groups may be straight-chain or branched; tri(alkyl)aryl phosphites such as triphenyl phosphite and tricresyl phosphite; and mixtures thereof. Spec ific examples of the salt of phosphorus-or phosphoric-esters are those obtained by allowing a monophosphate, a diphosphate, a triphosphate, a monophosphite, a diphosphite, or a triphosphite to react with a nitrogen-containing compound such as ammonia or an amine compound having in its molecules only hydrocarbon or hydroxyl-containing groups having 1 to 8 carbon atoms so as to neutralize the whole or part of the remaining acid hydrogen. The salt of phosphorus- or phosphoric-esters may be salts of divalent metals such as zinc and iron. Specific examples of the nitrogen-containing compound are ammonia; alkylamines, of which the alkyl group may be straight-chain or branched, such as monomethylamine, monoethylamine, monopropylamine, monobutylamine, monopentylamine, monohexylamine, monoheptylamine, monooctylamine, dimethylamine, methylethylamine, diethylamine, methylpropylamine, ethylpropylamine, dipropylamine, methylbutylamine, ethylbutylamine, propylbutylamine, dibutylamine, dipentylamine, dihexylamine, diheptylamine and dioctylamine; alkanolamines, of which the alkanol group may be straight-chain or branched, such as monomethanolamine, monoethanolamine, monopropanolamine, monobutanolamine, monopentanolamine, monohexanolamine, monoheptanolamine, monooctanolamine, monononanolamine, dimethanolamine, methanolethanolamine, diethanolamine, methanolpropanolamine, ethanolpropanolamine, dipropanolamine, methanolbutanolamine, ethanolbutanolamine, propanolbutanolamine, dibutanolamine, dipentanolamine, dihexanolamine, diheptanolamine and dioctanolamine; and mixtures thereof. These Components (E) may be used alone or in combination. In the present invention, Component (E) is preferably at least one member selected from the group consisting of monophosphates, diphosphates, monophosphites, diphosphates, thiophosphates, thiophosphites, and salts thereof and more preferably at least one member selected from the group consisting of monophosphites, diphosphites, and salts thereof. The carbon number of the hydrocarbon group of these compounds is preferably 4 to 20 and more preferably 6 to 18 . The lubricating oil composition can obtain the effects to be intended thereby without Component However, it was confirmed by a road performance test using a four-cycle motorcycle that when the number of revolutions of the engine is low, for example, l,000rpm, and high, for example, 10,000rpm, further improved fuel consumption efficiency could be achieved due to the presence of Component (E). Therefore, in such a case, the lubricating oil composition of the present invention preferably contains Component { E ) . The lower limit content of Component (E) in the lubricating oil composition of the present invention is preferably 0.005 percent by mass and more preferably 0.01 percent by mass in terms of phosphorus, based on the total mss of the composition. The upper limit content of Component (E) is 0.1 percent by mass, preferably 0.08 percent by mass, and more preferably 0.04 percent by mass in terms of phosphorus, based on the total mass of the composition. Component (E) exceeding the upper limit can not obtain the effect as expected and lower the phosphorus content in the resulting lubricating oil compos ition. Although the lubricating oil composition of the present invention is excellent in fuel consumption efficiency, i.e., low friction properties and friction properties in a wet clutch, conventional additives may be added to the composition for the purpose of further enhancing these properties. Such additives may be friction modifiers excluding Component (A), ashless dispersants excluding Component (B), metallic detergents excluding Component (C), extreme-pressure additives and anti-wear agent excluding Components (D) and {E) , oxidation inhibitors, rust preventives, corrosion inhibitors, viscosity index improvers, pour-point depressants, rubber swelling agents, antifoamers, and coloring agent. Examples of friction modifiers excluding Component (A) are aliphatic alcohols, fatty acids, fatty acid metal salts, fatty acid esters, aliphatic amines, aliphatic amine salts, and aliphatic amides. Although these friction modifiers are less effective in terms of fuel consumption efficiency than the molybdenum compounds, the use of such friction modifiers in place of or in combination with the molybdenum compounds to be used in the present invention can provide a lubricating oil composition with excellent fuel consumption efficiency and friction properties in a wet clutch. Examples of ashless dispersants excluding Component (B) are benzylamines, alkylpolyamines, polybuteneamines, and boron- or sulfur-modified products thereof, and alkenyl succinic acid esters. Examples of metallic detergents excluding Component (C) are alkali metal-based sulfonates, phenates, and salicylates and alkali metal-based or alkaline earth metal-based naphthenates, which may be used alone or in combination. The alkali metals may be sodium and potassium. Examples of extreme-pressure additives and anti-wear agents excluding Components (D) and (E) are sulfur-based compounds . Specific examples of the sulfur-based compounds are disulfides, olefin sulfides, and sulfide oils and fats. Examples of oxidation inhibitors are phenol- or amine-based compounds which are conventionally used in a lubricating oil. Specific examples of such oxidation inhibitors are alkylphenols such as 2-6-di-tert-buty1-4-methylphenol, bisphenols such as methylene-4,4-bisphenol(2,6-di-tert-butyl-4-methylphenol), naphtylamines such as phenyl-a-naphtylamine, dialkyldiphenylamines, dialkyldiphenylamines, and phenothiazines. Examples of rust preventives are alkenyl succinic acids, alkenyl succinic acid esters, polyhydric alcohol esters, petroleum sulfonates, and dinonylnaphthalenesulfonate. Examples of corrosion inhibitors are benzotriazole, thiadiazole, and imidazole compounds. Viscosity index improvers may be non-dispersion type or dispersion type viscosity index improvers. Specific examples are non-dispersion or dispersion type polymethacrylates and olefin copolymers, polyisobutenes, polystyrenes, ethylene-propylene copolymers, and styrene-diene copolymers and hydrides thereof. These viscosity index improvers have generally a weight-average molecular weight of 5,000 to 1,000,000. However, it is desired to use a viscosity index improvers having a weight-average molecular weight of 100,000 to 1,000,000, preferably 200,000 to 900,000, and particularly preferably 400,000 to 800,000 for further enhancing fuel consumption efficiency. In the case of using the lubricating oil of the present invention in a four-cycle motorcycle engine, particularly preferred are styrene-diene copolymers and hydrides thereof with the objective of enhancing shear stability. Examples of pour-point depressants are polymethacrylate-based polymers, alkylated aromatic compounds, fumarate-acetic acid vinyl copolymers, and ethylene-acetic acid vinyl copolymers. Examples of the antifoamers are silicones such as dimethylsilicone and fluorosilicone. No particular limitation is imposed on the amount of each of these additives. However, the antifoamer is added in an amount of 0.0005 to 0.01 percent by mass, the viscosity index improver is added in an amount of 0.05 to 20 percent by mass, the corrosion inhibitor is added in an amount of 0.005 to 0.2 percent by mass, and the other additives are added in an amount of 0.05 to 10 percent by mass, all being based on the total mass of the composition. The lubricating oil composition of the present invention is excellent not only in fuel consumption efficiency at from mid to high temperatures and friction properties in a wet clutch but also in anti-wear properties, high-temperature oxidation stability, and detergency and further has sufficient gualities conforming with the standards for four-cycle motorcycle engine oil defined by JASO (JASO T 903-98). One of the standards requires an engine oil to have a sulfated ash content of 1.2 percent by mass or less. The lubricating oil composition of the present invention can be made to be a low-ash type lubricating oil whose sulfated ash content is 1.0 percent by mass or less, further 0.8 percent by mass or less, and particularly 0.7 percent by mass or less, with excellent fuel consumption efficiency at from mid to high temperatures and extremely improved friction properties in a wet clutch. The term "sulfated ash content" used herein denotes a sulfated ash content measured in accordance with JIS K2272, i.e., an ash content determined by measuring the constant weight of the carbonized residue obtained by burning a sample and adding sulfuric acid thereto. The lubricating oil composition of the present invention contains phosphorus in an amount of 0.12 percent by mass or less, based on the total mass of the composition. However, the phosphorus content can be lowered to 0.1 percent by mass or less, further 0.08 percent by mass or less, and particularly 0.07 percent by mass or less by adjusting the amount of the components constituting the lubricating oil composition of the present invention. The phosphorus content of the composition of the present can be further reduced to 0.05 percent by mass or less by omitting Component (E) such that the composition is further improved in fuel consumption efficiency and friction properties in a wet clutch. In the case of using the composition of the present invention in a four-cycle motorcycle engine, it preferably contains Component (E) because of further improvement in fuel consumption efficiency as described with respect to Component (E). Such a low ash and phosphorus lubricating oil composition obtained by the present invention can be extremely reduced in harmful influences on exhaust gas purifying devices and thus can be used advantageously for automobiles equipped with a ternary catalyst, an oxidation catalyst, an EGR system, a DPF, and the like. The kinematic viscosity at 100°C of the lubricating oil composition of the present invention is preferably 5.6 mmVs or greater, more preferably 9.3 min'/s or greater and preferably 21.9 mmVs or less, more preferably 16.3 mm2/s or less, and particularly preferably 12.5 mm2 /s or less. This specified range of kinematic viscosity at 100°C can impart enhanced fuel consumption efficiency to a lubricating oil compos it ion - The lubricating oil composition of the present invention is suitable for internal combustion engines such as gasoline engines, diesel engines, and gas engines and particularly suitable for internal combustion engines equipped with an exhaust gas additional treatment device, power transmitting devices equipped with a wet clutch, and four-cycle motorcycles. However, the lubricating oil composition can be also used as one required to have fuel consumption efficiency and friction-adjusting capabilities, for examples as shock absorber oils. EXAMPLES Hereinafter, the present invention will be described in more detail by way of the following examples and comparative examples, which should not be construed as limiting the scope of the invention. [Examples 1 to 14 and Comparative Examples 1 and 2] The lubricating oil compositions of the present invention (Examples 1 to 14) and those for comparison {Comparative Examples 1 and 2) were prepared in accordance with the formulations shown in Table 2. The compositions of Examples 1 to 14 were those which were reduced in sulfated ash content and contained boron-containing and boron-free succinimides in arbitrary combination. The composition of Comparative Example 1 was a conventional alkaline earth metal salicylate-based fuel efficient engine oil, while the composition of Comparative Example 2 was a composition obtained by decreasing the amount of the alkaline earth metal salicylate of the composition of Comparative Example 1 such that the sulfated ash content was reduced to 0 .6 percent by mass or less . The following SRV friction test and clutch friction properties test were conducted so as to evaluate each of the compositions in terms of the fuel efficient properties at a temperature of from 80°C to 120°C and friction properties in a wet clutch. The results are shown in Table 1. [SRV Friction Test] The test was conducted by using an SRV friction test apparatus which has generally been used to evaluate the ability of an engine oil composition to provide fuel consumption efficiency. It has been found that the lower friction coefficient an engine oil is superior in fuel consumption efficiency. The friction coefficient of each composition was measured at a load of 400 N, a frequency of 50 Hz, an amplitude of 1.5 mm, and an oil temperature of from 80 °C to 120°C {every 10°C increase) . [Clutch friction properties test] JASO Motorcycles Four Cycle Engine Oil Standard (JASO T 903-98) specifies the physicochemical properties which are suitable for engine oils for a motorcycle four-cycle engine and the performance classification based on friction properties. More specifically, dynamic- and static-friction coefficient and stop time were measured by the test conditions in accordance with JASO T 904-98 so as to determine the dynamic- and static-friction indexes and stop time index in accordance with the calculation method described below. The resulting indexes were classified into MA or MB group in accordance with the values shown in Table 1. Group "MA" indicates that the engine oil compositions are excellent all in dynamic- and static-friction coefficient and stop time. Whereas Group "MB" indicates that the composition is lower in any of indexes than the standard and would be poor in the ability to prevent a clutch from slipping. Table 1 Performance and standard indexes of Motorcycles four-cycle engine oil Calculation method: (example : dynamic friction index) Dynamic friction index = 1 + (Ud(s) - Ud{B)) / (Md(k) - Ud(B)) wherein//d (s) : the dynamic friction coefficient of sample oil Ud(A) : the dynamic friction coefficient of JAFRE-A (high friction properties standard oil) Ud{B) : the dynamic friction coefficient of JAF"RE-B (low friction properties standard oil containing a friction modif ier) Static friction index and stop time index were determined in the same calculation method. *1: Aromatics: 6.3 mass%. Viscosity index: 122, Kinematic viscosity (100°C): 4.11 mmVs , NOACKvolatility: 14.5 mass% *2: Aromatics: 8.1 mass%, Viscosity index: 130, Kinematic viscosity (100"C): 6.56 mmVs, NOACK volatility: 6.9 mass! * 3 : Alkyl group: C8, Molybdenum content: 7.2 mass!, Phosphorus content: 5.5 mass% *4: Alkyl group: C8, Molybdenum content: 4.5 mass% *5 : Nitrogen content: 1.8 mass%, Boron content: 0.47 mass%, B/N ratio: 0.26 *6: Nitrogen content: 1.5 mass%, Boron content: 0.5 mass%, B/N ratio: 0.33 * 7 : Nitrogen content: 1.5 m a s s % , Boron content: 1.3 mass?, B/N ratio: 0.86 *8: Nitrogen content: 2.1 mas s % , Boron content: 0 mass%, B/N ratio: 0, mono type *9: Nitrogen content *. 1.8 mass%, Boron content: 0 mass%, B/N ratio: 0, bis type *10: Calcium content: 6.4 mass*, Total base number: 170 mgKOH/g *11: Calcium content: 9.0 massS, Total base number: 255 mgKOH/g * 1 2 : Petroleum-based calcium sulfonate, Calc ium content: 120 mass%, Total base number: 320 mgKOH/g *13: Ethylene oligomer-alky1 ated calcium sulfonate, Calcium content: 11.8 mass%, Total base number: 310 mgKOH/g *14: Alkyl group: C3-C8, Pri-ZDTP/Sec-ZDTP mass ratio: 20/80, Zinc content: 8.2 mass %, Total phosphorus content: 7.1 mass%, *15: Amine salt of alkylphosphate, Phosphorus content: 2.4 mass %, 16: including SDC/PMA viscosity index improver, phenol/amine-based oxidation inhibitor, and antifoamer From the results shown in Table 2, it was found that the composition of Comparative Example 1 containing calcium salicylate in an amount of 0.18 percent by mass in terms of calcium was a conventional engine oil which was excellent in fuel consumption efficiency at a temperature of 80"C but poor in fuel consumption efficiency at 100DC or higher. Furthermore, the composition was particularly low in static friction properties index indicating the friction properties in a wet clutch and could possibly cause clutch slippage at the timing of starting or gear change. The composition of Comparative Example 2 obtained by reducing the calcium salicylate content of the composition of Comparative Example 1 such that the sulfated ash content was made to 0.6 mass% was deteriorated in mid to high temperature (80 to 120 °C ) fuel consumption efficiency, comparing with the composition of Comparative Example 2. Furthermore, it was found that the composition of Comparative Example 2 was low in static friction properties index indicating the friction properties in a wet clutch. leading to poor starting and gear change properties and deteriorated in dynamic friction properties index and stop time index, leading to poor power transmission properties . As apparent from the results shown in Table 2, it was found that the compositions of Examples 1 to 9 which contain a boron-containing succinimide whose B/N ratio was 0.2 to 0.9 and a boron-free succinimide and each of whose sulfated ash content was the same as, similar to, or lower than that of the composition of Comparative Example 2 were each improved in mid to high temperature fuel consumption efficiency and in friction properties in a wet clutch, comparing Comparative Example 2. Particularly, the composition of Example 1 containing calcium salicylate was extremely improved in mid to high temperature fuel consumption efficiency, comparing with Comparative Example 2. The compositions of Examples 2 to 9 containing' calcium sulfonate and/or calcium phenate were improved particularly in high temperature fuel consumption efficiency and static friction properties index in a wet clutch. Among these compositions, those of Examples 4, 8, and 9 each containing a petroleum-based calcium sulfonate derived from a mineral oil-based alkyl aromatic sulfonated product and a boron-containing succinimide whose B/N ratio was high, i.e., 0.5 to 0.9 were effective to improve the static friction properties index. The composition of Example 6 containing calcium sulfonate alkylated with an ethylene oligomer was effective to enhance the fuel consumption efficiency at high temperatures, dynamic friction properties index, and stop timing index- In the case of using a boron-containing succinimide whose B/Nratio is low, i.e., 0.2 to 0.5 and amono succinimide in combination, it is preferred to use the above petroleum-based calcium sulfonate. The composition of Example 5 in which the amount of the petroleum-based calcium sulfonate was reduced to 0.07 percent by mass in terms of alkaline earth metal, based on the total mass of the composition and the sulfated ash content was reduced to 0 . 5 percent by mass or lower was excellent in mid to high temperature fuel efficiency consumption and classified into MA in accordance with the JASO standard for a four-cycle motorcycle engine oil, resulting in excellent anti-slipping properties in a wet clutch. The compositions of Examples 10 to 14 containing a boron-containing succinimide whose B/N ratio was 0.5 to 0.9 and a bis-type boron-free succinimide were each excellent in mid to high temperature fuel consumption efficiency and friction properties in a wet clutch. However, the compositions of Examples 11 to 13 containing calcium sulfonate alkylated with an ethylene oligomer were classified into MA in accordance with the JASO standard for a four-cycle motorcycle engine oil and thus found to be excellent in anti-slipping properties for a wet clutch. The composition of Example 12 in which Component (D) was reduced to 0.06 percent by mass in terms of zinc such that the phosphorus content was reduced to 0 . 1 percent by mass was improved particularly in high-temperature fuel consumption efficiency. The composition of Example 13 in which MoDTC was used instead of MoDTP so as to reduce the phosphorus content to 0.07 percent by mass, based on the total composition was surprisingly improved in anti-clutch slipping properties comparable to a standard oil containing no organic molybdenum compound which is the JAFRE^A standard oil with each friction properties index in a wet clutch of 2.0. The composition of Example 14 in which calcium salicylate was used instead of calcium sulfonate was extremely excellent and stable in mid to high temperature fuel consumption efficiency and classified into MA in accordance with the JASO standard for a four-cycle motorcycle engine oil, leading to excellent anti-slipping properties for a wet clutch. Although Table 2 does not indicate, the compositions of Examples 12, 13, and 14 were low in SRV friction coefficient, i.e., of 0.38 to 0.042, 0.040 to 0.042, and 0.37 to 0.38, respectively even at a temperature of 50 to 70°C and found to be comparable to or better than the compositions of Comparative Examples 1 and 2 having an SRV friction coefficient of 0.038 to 0.041 and 0.040 to 0.042, respectively. The lubricating oil composition of the present invention is excellent in fuel consumption efficiency at mid to high temperatures as well as the friction properties in a wet clutch. Particularly even in the case of reducing the sulfated ash content and phosphorus content, the lubricating oil composition can maintain such excellent properties. Therefore, the lubricating oil composition can be used suitably for an internal combustion engine required to have the fuel consumption efficiency resulting from the recent enhanced heat load, a four-cycle motorcycle lubricating engine oil, an engine oil for the engine of an automobile equipped with an exhaust gas purifying device. WE CLAIM : 1. A lubricating oil composition comprises a mineral base oil selected from the group consisting of paraffinic and naphthenic lubricating base oils and/or a synthetic base oil selected from the group consisting of poly-a-olefins and hydrides thereof, isobutene oligomer and hydrides thereof, isoparaffin, alkylbenzenes, alkylnaphthalenes, diesters, copolymers of a-olefins and diesters, polyol esters, dialkyldiphenyl ethers, and polyphenyl ether, (A) an organic molybdenum compound in an amount of from 0.003 to 0.1 percent by mass in terms of molybdenum, (B) a boron-containing succinimide and/or a boron-free succinimide in an amount of from 0.08 to 0.3 percent by mass in terms of nitrogen and in a mass ratio of the nitrogen content to the molybdenum content of Component (A) of 1.6 or greater, (C) alkaline earth metal detergent selected from the group consisting of alkaline earth metal sulfonates, alkaline earth metal phenates and alkaline earth metal salicylates in an amount of 0.01 to 0.16 percent by mass in terms of alkaline earth metal, (D) zinc dithiophosphate in an amount of 0.01 to 0.1 percent by mass in terms of zinc, and (E) at least one member selected from the group consisting of phosphoric esters, phosphorus esters, and salts thereof in an amount of 0.1 percent by mass or less in terms of phosphorus, based on the total mass of the composition, and the sulfated ash content of the composition being 1 percent by mass or less, based on the total mass thereof. 2. The lubricating oil composition as claimed in claim 1, wherein Component (A) is a molybdenum dithiocarbamate. 3. The lubricating oil composition as claimed in claim 1 or 2, wherein Component (B) comprises a boron-containing succinimide and/or a boron-free mono and/or bis succinimide and the amount of the boron-containing succinimide is from 0.005 to 0.2 percent by mass in terms of boron, based on the total mass of the composition. 4. The lubricating oil composition as claimed in any one of the preceding claims wherein Component (C) is contained in an amount of 0.01 to 0.07 percent by mass in terms of alkaline earth metal, based on the total mass of the composition. 5. The lubricating oil composition as claimed in any one of the preceding claims wherein Component (D) is contained in an amount of 0.01 to 0.06 percent by mass in terms of zinc based on the total mass of the composition. 6. The lubricating oil composition as claimed in any one of the preceding claims wherein the sulfated ash content in the composition is 0.7 percent by mass or less, based on the total mass of the composition. 7. The lubricating oil composition as claimed in any one of the preceding claims wherein the phosphorus content in the composition is 0.08 percent by mass or less, based on the total mass of the composition. 8. The lubricating oil composition as claimed in any one of the preceding claims wherein the B/N ratio of said boron-containing succinimide is from 0.2 to 0.9. 9. The lubricating oil composition as claimed in any one of the preceding claims wherein Component (C) is one or more members selected from the group consisting of alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. 10. The lubricating oil composition as claimed in any one of the preceding claims wherein it has a static friction properties index of 1.15 or greater. 11. The lubricating oil composition as claimed in any one of the preceding claims wherein it has a static friction properties index of 1.40 or greater. 12. The lubricating oil composition as claimed in any one of the preceding claims wherein it has a dynamic friction properties index, static friction properties index, and stop time index of 1.7 or greater, respectively. 13. The lubricating oil composition as claimed in any one of the preceding claims wherein it is classified into MA class in accordance with JASO T 903-98. 14. The lubricating oil composition as claimed in any one of the preceding claims wherein it is an engine oil for an automobiles equipped with an exhaust gas purifying system. 15. The lubricating oil composition as claimed in any one of the preceding claims wherein it is an engine oil for a four-cycle motorcycle engine. 16j The lubricating oil composition as claimed in claim 2, wherein said molybdenum dithiocarbamate is represented by the formula wherein R1, R2, R3, and R4 are each independently a hydrocarbon group having 1 to 24 carbon atoms, a is an integer of 0 to 4, b is an integer of 0 to 4, and a + b = 4. 17. A method for improving the performance of fuel consumption efficiency at from mid to high temperatures and / or friction properties in a wet clutch using __ the lubricating oil composition as claimed in any one of claims 1 to 16.

Documents:

0572-mas-2002 abstract duplicate.pdf

0572-mas-2002 abstract.pdf

0572-mas-2002 claims duplicate.pdf

0572-mas-2002 claims.pdf

0572-mas-2002 correspondences others.pdf

0572-mas-2002 correspondences po.pdf

0572-mas-2002 description (complete) duplicate.pdf

0572-mas-2002 description (complete).pdf

0572-mas-2002 form-18.pdf

0572-mas-2002 form-3.pdf

0572-mas-2002 form-5.pdf

0572-mas-2002 petition.pdf