JPWO2014156325A1 - Lubricating oil composition - Google Patents

Abstract

Provided is a lubricating oil composition that does not generate precipitates even during long-term storage, has excellent fuel efficiency, and is excellent in wet clutch friction characteristics. (A) Composition of (B) organomolybdenum compound in a lubricating base oil having a kinematic viscosity at 100 ° C. of 2.5 to 20 mm 2 / s and an aromatic content of two or more rings of 0.4% by mass or more. 0.075 to 0.1% by mass as molybdenum element equivalent on the basis of the total amount of matter, and (C) boron-containing succinimide and / or succinimide not containing boron, (D) alkaline earth metal detergent, (E) A lubricating oil composition containing zinc dithiophosphate.

Description

  The present invention relates to a lubricating oil composition, in particular, an engine lubricating oil composition, and more particularly to a lubricating oil composition that is excellent in friction characteristics of a wet clutch in addition to low fuel consumption, and that is particularly suitable for a four-cycle engine for a motorcycle. It is.

Low fuel consumption of automobiles, which has begun to be implemented in the wake of the oil crisis, is still one of the important issues from the viewpoint of resource protection and environmental protection, and its needs have been increasing in recent years. Automobile fuel efficiency has been improved by reducing the weight of the vehicle body, improving the combustion of the engine, and reducing the friction of the engine and drive system. Reducing engine friction includes improving the valve train mechanism, reducing the surface roughness of the sliding member, and using fuel-efficient engine oil.
Among these, the use of low fuel consumption engine oil is becoming more popular in the market because of its cost effectiveness. As measures to reduce fuel consumption due to engine oil, lowering the viscosity with the aim of reducing friction loss under fluid lubrication conditions such as piston systems and bearings is being studied, and also under mixed lubrication and boundary lubrication such as valve systems. It is considered essential to add a friction reducing agent such as an organomolybdenum compound intended to reduce friction loss.

In addition to the engine, the lubricating oil used in a four-cycle engine for a motorcycle in which a transmission and a power transmission part (wet clutch) of the transmission are housed in a single crankcase are required for both engine oil and transmission oil. It is necessary to satisfy the performance, and the demand for fuel saving performance is increasing as described above. The above-described engine, drive unit, and four-cycle engine for motorcycles are further reduced in size, weight, and output, and accordingly, the heat load on the lubricating oil used in these engines is higher than ever and the high temperature is increased. There is also a tendency for fuel efficiency to be emphasized.
In particular, a four-cycle engine for a motorcycle has a wider engine speed range than that of a four-wheeled vehicle, and has a high normal speed. The engine oil temperature fluctuates greatly from low to high depending on the driving conditions. There is a demand for engine oil having stable fuel-saving performance.

As a fuel-saving engine oil, for example, in Patent Document 1, a specific additive (alkaline earths) is added to a base oil having a kinematic viscosity at 100 ° C. of ² to 8 mm ² / s and an aromatic content of 15% by mass. Engine oil compositions containing specific amounts of metal salicylate detergents, molybdenum dithiocarbamate friction reducers and the like have been proposed.
However, when general fuel-saving engine oil is applied as it is to a four-cycle engine for a motorcycle, the slippage of the wet clutch is remarkable and not only the power transmission capability of the clutch is inferior, but also the shift feeling is deteriorated, the friction material is heated, There has been a common sense of those skilled in the art that there is concern about the occurrence of burning, wear, breakage, etc., and it is extremely difficult to achieve both fuel saving and prevention of slippage of the wet clutch. Therefore, the use of such fuel-saving engine oil has been applied only to special motorcycles that have a clutch slip countermeasure.
On the other hand, Patent Document 2 discloses a specific additive (zinc dialkyldithiophosphate, metal-based cleaning agent) for a base oil having a kinematic viscosity at 100 ° C. of 3 to 10 mm ² / s or a mixed base oil containing 15% by mass or more thereof. A four-cycle engine oil composition for motorcycles containing an agent, a friction modifier and the like has been proposed. However, this four-cycle engine oil composition for motorcycles has reduced fuel consumption and has excellent fuel economy performance over an engine speed of 3000 to 13000 rpm. Sulfurized oxymolybdenum dioctyldithiophosphate as a friction modifier is In consideration of clutch slip, only 0.62% by mass (when the concentration of molybdenum element is 10% by mass, the amount converted to molybdenum element is 620 ppm by mass) is added, resulting in a somewhat inferior fuel economy effect. was there.
The JASO motorcycle four-cycle oil standard (T903: 2011) classifies engine oil performance into three types, MA1, MA2 and MB, based on clutch performance, and requires appropriate use according to the vehicle. Therefore, a four-cycle engine oil for two-wheeled vehicles that is widely used and that is excellent in fuel efficiency at medium to high temperatures and excellent in friction characteristics of a wet clutch is desired.

JP-A-8-302378 JP 2000-087070 A

Molybdenum compounds that are highly effective in reducing the friction coefficient between metals are often used for fuel-saving oils. However, a lubricating oil simply containing a large amount of a molybdenum compound has a low friction coefficient of the clutch, and cannot retain the clutch performance for a motorcycle described above. Further, when the amount of molybdenum used is increased, the effect of reducing friction is increased. However, when a molybdenum compound is blended with a low-viscosity base oil, a problem occurs that precipitates are generated even during long-term storage.
It is an object of the present invention to provide a lubricating oil composition that has excellent fuel efficiency, satisfies clutch performance, and does not generate precipitates even during long-term storage.

  As a result of intensive studies to solve the above problems, the present inventors have found that a lubricating oil composition having a specific configuration satisfies a clutch performance while containing a larger amount of a molybdenum compound, and can be used during long-term storage. In addition, the inventors have found that no precipitate is generated, the product has an excellent long life, and an excellent fuel efficiency, and the present invention has been completed.

The present invention provides (A) a lubricating base oil having a kinematic viscosity at 100 ° C. of 2.5 to ²⁰ mm ² / s and an aromatic content of two or more rings of 0.4% by mass or more. 750 to 1000 ppm by mass, based on the total amount of the organomolybdenum compound based on the composition, (C) boron-containing succinimide and / or succinimide not containing boron, (D) alkaline earth metal detergent (E) A lubricating oil composition containing zinc dithiophosphate.
The lubricating oil composition preferably further contains at least one selected from (F) phosphoric esters, phosphites, and salts thereof.
Moreover, it is preferable that the kinematic viscosity at 100 degreeC of the (A) lubricating base oil of the said lubricating oil composition is 3-9 mm < ² > / s.
Further, (C) boron-containing succinimide and / or succinimide not containing boron in the lubricating oil composition is preferably 0.08 to 0.3% by mass in terms of nitrogen element.
The (D) alkaline earth metal detergent in the lubricating oil composition is preferably 0.01 to 0.16% by mass in terms of alkaline earth metal element.
Further, the (E) zinc dithiophosphate of the lubricating oil composition preferably contains 0.01 to 0.1% by mass in terms of zinc element.
The (F) (sub) phosphates of the lubricating oil composition contain at least one selected from phosphoric esters, phosphites and salts thereof in an amount of 0.1% by mass in terms of phosphorus element. The following is preferable.
Further, the sulfated ash content of the lubricating oil composition is preferably 1% by mass or less.

  The lubricating oil composition of the present invention has an excellent effect that it has excellent fuel efficiency, is satisfactory in clutch performance, and does not generate precipitates even after long-term storage.

Hereinafter, the present invention will be described in detail.
When the lubricating base oil (A) in the present invention has a kinematic viscosity at 100 ° C. of 2.5 to ²⁰ mm ² / s and an aromatic content of 2 or more rings is 0.4% by mass or more, It is not particularly limited, and any mineral oil or synthetic oil can be used as long as it is usually used as a lubricating base oil for engine oil compositions.
Kinematic viscosity at 100 ° C. of the lubricating base oil (A) is preferably in the range of 3~9mm ² / s, and is more preferably 3.5 mm ² / s or more, more preferably 4.0mm ² / s or more, and even more preferably 4.5 mm ² / s or more. Moreover, 8 mm < ² > / s or less is preferable, More preferably, it is 7.5 mm < ² > / s or less, More preferably, it is 7 mm < ² > / s or less, Especially preferably, it is 6.7 mm < ² > / s or less.
When the kinematic viscosity at 100 ° C. is less than 2.5 mm ² / s, the clutch performance is lowered, and precipitates are likely to be generated during long-term storage, and when it exceeds 20 mm ² / s, the fuel efficiency is reduced. In addition, the low temperature viscosity characteristics deteriorate. On the other hand, when the kinematic viscosity is less than 2.5 mm ² / s, the formation of an oil film at the lubrication point becomes insufficient, resulting in poor lubricity and an increase in the evaporation loss of the lubricating base oil.

Furthermore, the aromatic content of two or more rings in the lubricating base oil (A) is preferably 0.5% by mass or more, more preferably 0.6% by mass or more. When the aromatic content of two or more rings of the lubricating base oil (A) is less than 0.4% by mass, the high temperature cleanability and coking resistance (heat resistance) of the lubricating oil composition cannot be sufficiently improved. . From the viewpoint of thermal stability, the aromatic content of the two or more rings is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

In the present invention, the kinematic viscosity at 100 ° C. refers to the kinematic viscosity at 100 ° C. defined in ASTM D-445, and the aromatic content of two or more rings is high performance liquid chromatography (HPLC) ( Atsushi Matsunaga, Anal. Chem. 1983, 55, 1375-1379 (see “Separation of Aromatic and Polar Compounds in Fossil Fuel Liquids by Liquid Chromatography”).

  The lubricating base oil (A) of the present invention preferably has a viscosity index of 80 or more, more preferably 85 or more, and particularly preferably 90 or more. When the viscosity index of the base oil is less than 80, the viscosity at a low temperature increases and the startability may be deteriorated. In the present invention, the viscosity index means a viscosity index measured according to JIS K2283-1993.

Further, the NOACK evaporation amount of the lubricating base oil (A) of the present invention is preferably 20% by mass or less, more preferably 16% by mass or less, and particularly preferably 10% by mass or less. By setting the NOACK evaporation amount of the lubricating base oil to 20% by mass or less, the lubricating oil has a smaller evaporation loss under high temperature conditions and can avoid adverse effects due to accumulation in the exhaust gas purification device, the piston and the combustion chamber. It becomes possible to obtain a composition. The NOACK evaporation amount referred to here is the evaporation amount when 60 g of the lubricating oil sample is evaporated under the conditions of 250 ° C., −20 mmH ₂ O for 1 hour in accordance with CEC L-40-T-87. Means.

As long as the lubricating base oil in the present invention satisfies the above-mentioned lubricating base oil conditions, the above-described mineral base oil or synthetic base oil can be used alone, and two or more mineral base oils, Alternatively, it may be a mixture of two or more kinds of synthetic base oils, and may be a mixture of mineral oil base oils and synthetic base oils. And the mixing ratio of 2 or more types of base oil in the said mixture can be chosen arbitrarily.
As mineral base oils, lubricating oil fractions obtained by subjecting crude oil to atmospheric distillation and reduced pressure distillation are subjected to solvent deburring, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydrorefining, sulfuric acid Examples thereof include paraffinic and naphthenic lubricating base oils and the like, which are refined by appropriately combining purification treatments such as washing and clay treatment.

  Synthetic base oils include poly-α-olefins (eg polybutene, 1-octene oligomers, 1-decene oligomers, ethylene-propylene oligomers) or their hydrides, isobutene oligomers or their hydrides, isoparaffins, alkylbenzenes, alkyls Naphthalene, diesters (eg, dibutyl maleate, ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate), co-weight of α-olefin and diester Coalesces, polyol esters (eg, trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritol pelargo Examples thereof), dialkyl diphenyl ether, polyphenyl ether and the like.

  The lubricating base oil (A) of the present invention comprises a base oil (A-1) having a saturated hydrocarbon content of 90% or more and a base oil (A-2) having a saturated hydrocarbon content of less than 90% by mass. It preferably consists of a mixture.

The kinematic viscosity at 100 ° C. of the base oil (A-1) is preferably 2.0 mm ² / s or more, more preferably 3.0 mm ² / s or more, and more preferably 3.5 mm ² / s. s or more, particularly preferably 4.0 mm ² / s or more. Moreover, 13 mm < ² > / s or less is preferable, More preferably, it is 10 mm < ² > / s or less, More preferably, it is 8 mm < ² > / s or less, Especially preferably, it is 7 mm < ² > / s or less.
When the kinematic viscosity at 100 ° C. of the base oil (A-1) exceeds 13 mm ² / s, the low-temperature viscosity characteristics deteriorate, whereas when the kinematic viscosity is less than 2.0 mm ² / s, the lubrication point Insufficient oil film formation at this point results in poor lubricity and increases the evaporation loss of the lubricating base oil.

In addition, the base oil (A-1) is preferably a base oil classified into group II and group III based on a base oil classification by API (American Petroleum Institute) and a base oil obtained by isomerizing wax. .
In the present invention, the saturated hydrocarbon content means a value measured by ASTM D-2007.

  Although there is no restriction | limiting in particular about the manufacturing method of the said base oil (A-1), The atmospheric pressure residual oil obtained by carrying out atmospheric pressure distillation of crude oil is desulfurized, hydrocracked, and fractionated to the set viscosity grade Alternatively, the residual oil is preferably dewaxed or catalytically dewaxed, and if necessary, further extracted with a solvent and hydrogenated to form a base oil.

  In recent years, the above base oil (A-1) has also been subjected to a process such as solvent refining and hydrorefining after solvent distillation under reduced pressure and fractional distillation to the required viscosity grade, In the base oil production process produced by dewaxing, GTL produced by the petroleum wax isomerized lubricating base oil obtained by hydroisomerizing petroleum wax, which is a secondary product in the dewaxing process, the Fischer-Tropsch process, etc. Also included are GTL wax isomerized lubricating base oils and the like produced by a technique of isomerizing WAX (gas-trimmed wax). In this case, the basic production process of the wax isomerized lubricating base oil is the same as that of the hydrocracking base oil.

The% C _A of the base oil (A-1), is not particularly limited, is preferably less than 3, more preferably 2 or less, even more preferably 1 or less, and most preferably substantially 0 is there. If it exceeds 10, the improvement of heat resistance, which is one of the objects of the present invention, becomes insufficient.
Note that the% _{C A} dove means a value measured by a method in accordance with ASTM D3238-85 (n-d-M ring analysis).

Further, the sulfur content of the base oil (A-1) is not particularly limited, but in one embodiment is 0.03 mass% or less, and in another embodiment is 0.01 mass% or less, In yet another embodiment, the base oil (A-1) is substantially free of sulfur. Here, the smaller the sulfur content, the higher the degree of purification, and the problem of sludge solubility is less likely to occur.
Although there is no restriction | limiting in particular in the measuring method of a sulfur content, JISK2541-1996 etc. are generally used.

  The blending amount of the base oil (A-1) is preferably 45% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and most preferably, based on the total amount of the base oil. 80% by mass or more. Moreover, Preferably it is 95 mass% or less, More preferably, it is 90 mass% or less.

On the other hand, the kinematic viscosity at 100 ° C. of the base oil (A-2) is 3 mm ² / s or more, preferably 6 mm ² / s or more, particularly preferably 9 mm ² / s or more. Moreover, it is 60 mm < ² > / s or less, Preferably it is 40 mm < ² > / s or less, Most preferably, it is 35 mm < ² > / s or less. When the kinematic viscosity at 100 ° C. of the base oil (A-2) exceeds 60 mm ² / s, the workability is lowered, whereas when the kinematic viscosity at 100 ° C. is less than 3 mm ² / s, Insufficient oil film formation results in poor lubricity and increases the evaporation loss of the lubricating base oil.

  The base oil (A-2) preferably has a saturated hydrocarbon content of less than 90% by mass. When the saturated hydrocarbon content of the base oil (A-2) is 90% by mass or more, it is difficult to suppress the precipitation of the molybdenum compound.

  As the base oil (A-2), generally, the atmospheric distillation residue is further distilled under reduced pressure, fractionated to the required viscosity grade, and then subjected to solvent refining, hydrorefining and other processes to remove the solvent. Base oils produced by wax are preferred.

The aromatic content of the base oil (A-2) is not particularly limited, but is preferably 3% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and most preferably. Is 30% by mass or more. Moreover, 80 mass% or less is preferable, 60 mass% or less is more preferable, and 50 mass% or less is further more preferable. This aromatic content is a value measured according to JIS K2536-1.
If the aromatic content is less than 3% by mass, it is difficult to suppress the precipitation of the molybdenum compound. On the other hand, if it exceeds 80% by mass, the heat resistance is lowered and the lubricating oil composition of the present invention cannot exhibit sufficient performance.

The aromatic content of the two or more rings of the base oil (A-2) is not particularly limited, but is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more. Yes, and most preferably 30% by mass or more. Moreover, 50 mass% or less is preferable, 45 mass% or less is more preferable, and 40 mass% or less is further more preferable.
If the aromatic content of two or more rings is less than 3% by mass, it is difficult to suppress the precipitation of the molybdenum compound of the present invention. On the other hand, if it exceeds 50% by mass, the heat resistance is lowered and the lubricating oil composition of the present invention cannot exhibit sufficient performance.

The blending amount of the above base oil (A-2) is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 30% by mass or less, and still more preferably based on the total amount of the base oil. Is 20% by mass or less, and most preferably 10% by mass or less. Moreover, 3 mass% or more is preferable on a base oil whole quantity basis, More preferably, it is 5 mass% or more.
When it exceeds 60 mass%, heat resistance will fall and sufficient performance as a lubricating oil composition of this invention cannot be exhibited. If it is less than 3%, precipitation of the molybdenum compound cannot be sufficiently suppressed.

  Examples of the (B) organic molybdenum compound in the present invention include molybdenum dithiocarbamate and molybdenum dithiophosphate. Specific examples of molybdenum dithiocarbamate include compounds represented by the following general formula (1). Specific examples of molybdenum dithiophosphate include compounds represented by the following general formula (2).

In the general formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrocarbon group having 1 to 24 carbon atoms, and a and b are a = 0 to 4, b = 0. -4 and an integer where a + b = 4.

In the general formula (2), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrocarbon group having 1 to 24 carbon atoms, and c and d are c = 0 to 4, d = 0. -4 and c + d = 4 represents an integer.

Formula ^{R 1,} R 2, ^{R 3} and ^{R 4,} and the general formula ^{R 5,} R 6, ^{R 7} and hydrocarbon group having 1 to 24 carbon atoms represented by ^{R 8} in (2) (1) Preferable examples include a linear or branched alkyl group having 1 to 24 carbon atoms, a cycloalkyl group having 5 to 13 carbon atoms, or a linear or branched alkylcycloalkyl group, each having 3 carbon atoms. -24 linear or branched alkenyl groups, C6-C18 aryl groups, linear or branched alkylaryl groups, C7-19 arylalkyl groups, and the like. The alkyl group or alkenyl group may be primary, secondary, or tertiary.

  In addition to the above, the organic molybdenum compound in the lubricating oil composition of the present invention includes, for example, basic nitrogen compounds such as succinimide, acidic molybdenum compounds such as molybdenum trioxide, and sulfur compounds such as hydrogen sulfide and phosphorus pentasulfide. An organic molybdenum complex which is the reaction product of is also a preferred example.

  In the lubricating oil composition of the present invention, the content of the organomolybdenum compound is 0.075% by mass or more, preferably 0.08% by mass or more in terms of molybdenum element, based on the total amount of the composition. When the content of the organomolybdenum compound is less than 0.075% by mass in terms of molybdenum element, a remarkable fuel saving effect cannot be obtained, while the content of the organomolybdenum compound is 0 in terms of molybdenum element. When the amount exceeds 0.1% by mass, an improvement in fuel saving effect corresponding to the content cannot be obtained, and the frictional characteristics of the wet clutch are deteriorated.

  In the lubricating oil composition of the present invention, molybdenum dithiophosphate and molybdenum dithiocarbamate are preferably used. However, the synergistic effect with other components improves fuel economy performance from low to high temperatures, and friction characteristics in wet clutches. In particular, molybdenum dithiocarbamate is particularly preferable.

  (S) As a succinimide which does not contain boron as the component (C), a monosuccinimide represented by the following general formula (3), a bissuccinimide represented by the general formula (4), and these are oxygenated organic compounds. Denatured ones can be exemplified.

In the general formula (3) or ^(4), R ^{10, R 11} and ^{R 12} each independently show a polybutenyl group, n represents an integer of 2-7.

The polybutenyl group represented by R ¹⁰ , R ¹¹ and R ¹² preferably has a number average molecular weight of 700 or more, more preferably 900 or more, while the number average molecular weight of the polybutenyl group is 3500 or less. It is preferable that there is, more preferably 1500 or less. By setting the number average molecular weight to 700 or more, it becomes possible to obtain a lubricating oil composition that is more excellent in cleanliness and dispersibility. On the other hand, by setting the number average molecular weight to 3500 or less, it becomes possible to obtain a lubricating oil composition having better low temperature fluidity. From the viewpoint of excellent sludge suppression effect, the lower limit value of n is 2, preferably 3, while the upper limit value of n is 7, preferably 6.

  Here, the polybutenyl group can be obtained from polybutene (polyisobutene) obtained by polymerizing a mixture of 1-butene and isobutene or high-purity isobutene with a catalyst such as aluminum chloride or boron fluoride. What has a vinylidene structure is contained normally 5-100 mol%. Further, as this polybutene (polyisobutene), it is also possible to use a product obtained by removing a trace amount of remaining fluorine and chlorine by an appropriate treatment method due to the catalyst in the production process. The content of halogen elements such as chlorine is preferably 50 ppm by mass or less, more preferably 10 ppm by mass or less, still more preferably 5 ppm by mass or less, and particularly preferably 1 ppm by mass or less.

  There is no restriction | limiting in particular in the manufacturing method of succinimide represented by General formula (3) or (4). For example, polybutenyl succinic acid obtained by reacting chlorinated polybutene, preferably polybutene from which chlorine and fluorine have been sufficiently removed, with maleic anhydride at 100 to 200 ° C. is converted into diethylenetriamine, triethylenetetramine, tetra A method of reacting with a polyamine such as ethylenepentamine or pentaethylenehexamine can be used. In the case of producing bissuccinimide, the polybutenyl succinic acid may be reacted twice as much as the polyamine (molar ratio). In the case of producing monosuccinimide, the polybutenyl succinic acid and the polyamine are used. May be reacted in an equal amount (molar ratio).

  Further, the succinimide not containing boron is, for example, a part of the amino group and / or imino group remaining by acting an oxygen-containing organic compound or the like on the compound represented by the general formula (3) or (4) The whole may be neutralized or amidated. Specific examples of the oxygen-containing organic compound include formic acid, acetic acid, glycolic acid, propionic acid, lactic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecyl acid, C 1-30 monocarboxylic acids such as lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, oleic acid, nonadecanoic acid, eicosanoic acid; oxalic acid, phthalic acid, trimellitic acid And C2-C30 polycarboxylic acids such as pyromellitic acid or their anhydrides or ester compounds; C2-C6 alkylene oxides; hydroxy (poly) oxyalkylene carbonates, and the like. When such an oxygen-containing organic compound is allowed to act, for example, when a part or all of the amino group or imino group in the compound of the general formula (3) or (4) has a structure represented by the following general formula (5) Presumed.

Here, R ¹³ represents a hydrogen atom, an alkyl group having 1 to 24 carbon atoms, an alkenyl group, an alkoxy group, or a hydroxy (poly) oxyalkylene group represented by —O— (R ¹⁴ O) _m H, and R ¹⁴ Represents an alkylene group having 1 to 4 carbon atoms, and m represents an integer of 1 to 5.

  On the other hand, the boron-containing succinimide as the component (C) is obtained by allowing a boron compound to act on the compound of the general formula (3) or (4). Examples of the boron compound include boric acid, borates, and borate esters. Specific examples of boric acid include orthoboric acid, metaboric acid, and tetraboric acid. Examples of borates include alkali metal salts, alkaline earth metal salts, and ammonium salts of boric acid.

  The boron-containing succinimide used in the present invention is not particularly limited in the mass ratio (B / N ratio) between the boron content and the nitrogen content, but is preferably 0.2 or more, more preferably 0.3 or more, More preferably, it is 0.5 or more, while it is preferably 1.2 or less, more preferably 1 or less, and still more preferably 0.9 or less. When the B / N ratio is less than 0.2, the effect of the present invention is small. On the other hand, when the B / N ratio exceeds 1.2, the oxidation stability is inferior.

  In the present invention, as the component (C), the boron-containing succinimide and the mono- or bissuccinimide not containing boron can be used alone, but the friction characteristics in the wet clutch can be further improved. It is preferable to use the boron-containing succinimide alone or in combination with the boron-containing succinimide and the mono- and / or bis-succinimide not containing boron. A preferable mixing ratio (mass ratio) in the case of using a boron-containing succinimide and a succinimide not containing boron is 100: 0 to 20:80 in the former: latter, and more preferably 90: 10-40. : 60, and particularly preferably 70:30 to 45:55.

  The content of the component (C) in the present invention is preferably 0.08% by mass or more, more preferably 0.09% by mass or more in terms of nitrogen element, based on the total amount of the composition, while preferably 0%. It is 0.3 mass% or less, More preferably, it is 0.2 mass% or less. When the content of component (C) is less than 0.08% by mass in terms of nitrogen element, based on the total composition, the fuel economy at medium and high temperatures and the friction characteristics in wet clutches are not sufficiently improved. On the other hand, when the content exceeds 0.3% by mass in terms of nitrogen element based on the total amount of the composition, there is a risk that fuel economy, low temperature viscosity characteristics and demulsibility may deteriorate. It is not preferable.

  For the same reason, the content of the boron-containing succinimide is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, still more preferably in terms of boron element based on the total composition. 0.02% by mass or more. On the other hand, in terms of boron element based on the total amount of the composition, it is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, still more preferably 0.08% by mass or less, and particularly preferably 0.05% by mass. It is as follows. If the boron-containing succinimide content exceeds 0.2% by mass, the fuel economy, low-temperature viscosity characteristics and anti-emulsification properties may be deteriorated, and there is concern about the effect on the exhaust gas purification device. Is not preferable.

  In the lubricating oil composition of the present invention, the mass ratio of the nitrogen element equivalent of the component (C) to the molybdenum element equivalent of the component (B) is preferably 1.6 or more, and is 1.8 or more. It is more preferable that it is 2.1 or more. On the other hand, the mass ratio is preferably 100 or less, more preferably 10 or less, further preferably 5 or less, and particularly preferably 4 or less. If the mass ratio is less than 1.6, the fuel saving performance particularly at high temperatures may be reduced, and the friction characteristics of the wet clutch may not be sufficiently improved. On the other hand, if the mass ratio exceeds 100, sufficient fuel saving performance may be obtained. Each of them is not preferable because it may not be obtained.

  The alkaline earth metal detergent as component (D) includes alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. In the present invention, one or two or more alkaline earth metal detergents selected from the group consisting of these can be used.

  Alkaline earth metal sulfonates include alkyl earth sulfonic acid alkaline earth metal salts obtained by sulfonated alkyl aromatic compounds having a molecular weight of 300 to 1500, preferably 400 to 700, particularly magnesium salts and / or calcium. It is a salt, and a calcium salt is preferably used. Specific examples of the alkyl aromatic sulfonic acid include so-called petroleum sulfonic acid and synthetic sulfonic acid. As said petroleum sulfonic acid, what sulfonated the alkyl aromatic compound of the lubricating oil fraction of mineral oil, what is called mahoganic acid etc. byproduced at the time of white oil manufacture are generally used. As the synthetic sulfonic acid, for example, a straight chain obtained as a by-product from an alkylbenzene production plant that is a raw material for detergents or obtained by alkylating an oligomer of an olefin having 2 to 12 carbon atoms (ethylene, propylene, etc.) to benzene. A sulfonated alkylbenzene having a linear or branched alkyl group or a sulfonated alkylnaphthalene such as dinonylnaphthalene is used. The sulfonating agent for sulfonating these alkyl aromatic compounds is not particularly limited, but fuming sulfuric acid or sulfuric anhydride is usually used. In the present invention, among these alkaline earth metal sulfonates, petroleum-based ones are particularly effective in improving fuel efficiency at medium and high temperatures and static friction characteristics in wet clutches, and synthetic ones are fuel-efficient at high temperatures. Since there is an effect of particularly improving the performance, dynamic friction characteristics and braking time characteristics, they can be used as needed.

  Alkaline earth metal phenates include, for example, alkylphenols, alkylphenol sulfides, alkaline earth metal salts of Mannich reactants of alkylphenols, particularly magnesium salts and calcium salts. Specific examples include those represented by the following general formulas (6) to (8).

In the general formulas (6), (7), and (8), R ²¹ , R ²² , R ²³ , R ²⁴ , R ^25, and R ²⁶ may be the same or different and each has 4 to 30 carbon atoms. , Preferably 6-18 linear or branched alkyl groups, M ¹ , M ² and M ³ each represent an alkaline earth metal, preferably calcium or magnesium, and x represents 1 or 2.

  In the present invention, these alkaline earth metal phenates can be preferably used because they can improve fuel economy from low to high temperatures and improve friction characteristics in wet clutches.

  Examples of the alkaline earth metal salicylates include alkaline earth metal salts of allyl salicylic acid, particularly magnesium salts and calcium salts. Specific examples include compounds represented by the following general formula (9).

In the general formula (9), R ²⁷ represents a linear or branched alkyl group having 4 to 30 carbon atoms, preferably 6 to 18 carbon atoms, and M ⁴ represents an alkaline earth metal, preferably calcium or magnesium. The alkyl group represented by R ²⁷ may be linear or branched. These may also be primary alkyl groups, secondary alkyl groups or tertiary alkyl groups. In the present invention, it can be preferably used because it can greatly improve the fuel efficiency and the friction characteristics of the wet clutch from low to high temperatures.

  Alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates can be obtained by directly using the above-mentioned alkyl aromatic sulfonic acids, alkylphenols, alkylphenol sulfides, Mannich reactants of alkylphenols, alkylsalicylic acid, etc., magnesium and / or calcium. It can be obtained by reacting with an alkaline earth metal base such as an alkaline earth metal oxide or hydroxide, or by replacing it with an alkaline earth metal salt such as a sodium salt or potassium salt, and then substituting it with an alkaline earth metal salt. Neutral (normal salt) alkaline earth metal sulfonates, neutral (normal salt) alkaline earth metal phenates and neutral (normal salt) alkaline earth metal salicylates; or neutral alkaline earth metal sulfonates, neutral alkaline earth Metal phenates and medium Basic alkaline earth metal sulfonate, basic alkaline earth metal phenate and basic alkali obtained by heating alkaline earth metal salicylate and excess alkaline earth metal salt or alkaline earth metal base in the presence of water Earth metal salicylates; and in the presence of neutral alkaline earth metal sulfonates, neutral alkaline earth metal phenates and neutral alkaline earth metal salicylates, alkaline earth metal hydroxides and carbon dioxide or boric acid Also includes overbased (superbasic) alkaline earth metal sulfonates, overbased (superbasic) alkaline earth metal phenates and overbased (superbasic) alkaline earth metal salicylates obtained by reacting It is.

  In the present invention, the above-mentioned neutral alkaline earth metal salts, basic alkaline earth metal salts, overbased (superbasic) alkaline earth metal salts, and mixtures thereof can be used. Alkaline earth metal detergents are usually commercially available in a state diluted with a light lubricating base oil or the like, and are available, but generally the metal content is 1.0 to 20% by mass. Preferably, 2.0 to 16% by mass is used. The total base number of the alkaline earth metal detergent used in the present invention is arbitrary, but the total base number is usually 500 mgKOH / g or less, preferably 150 to 450 mgKOH / g. The total base number means the total base number by the perchloric acid method measured in accordance with 7. of JIS K2501 (1992) "Petroleum products and lubricants-neutralization number test method".

  In the present invention, the content of the alkaline earth metal detergent as the component (D) is preferably 0.01% by mass or more, more preferably 0, in terms of alkaline earth metal element, based on the total amount of the composition. 0.02 mass% or more, more preferably 0.04 mass% or more. On the other hand, it is preferably 0.16% by mass or less, and this enables low ashing, but it is more preferably 0.13% by mass or less, further preferably 0.12% by mass or less, and 0.1% by mass. It is particularly preferable that the content be 07% by mass or less. When the content of the component (D) is less than 0.01% by mass, the fuel-saving performance at medium and high temperatures and the friction characteristics of the wet clutch may be deteriorated. On the other hand, when the content exceeds 0.16% by mass Although the friction characteristics of the wet clutch are improved, low ash oil cannot be obtained, and there is concern about accumulation in the exhaust gas purification device and the combustion chamber, which is not preferable.

  Specific examples of the component (E) zinc dithiophosphate include compounds represented by the following general formula (10).

In the general formula (10), R ³¹ , R ³² , R ³³ and R ³⁴ each independently represent a hydrocarbon group having 1 to 24 carbon atoms.
The hydrocarbon group having 1 to 24 carbon atoms represented by R ³¹ , R ³² , R ³³ and R ³⁴ is represented by R ¹ , R ² , R ³ and R ⁴ in the general formula (1) described above. It is synonymous with the example of a C1-C24 hydrocarbon group, and its preferable example is also the same.

  These zinc dialkyldithiophosphates and zinc dialkylphenyldithiophosphates may be compounds having different numbers of carbon atoms or different alkyl structures in one molecule. In the present invention, the component (E) 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) is preferably the former: the latter is preferably 5:95 to 50:50, more preferably 10:90 to 40:60. By setting the mixing ratio within the above preferable range, not only the effect of the present invention can be obtained, but also a composition excellent in wear prevention performance can be obtained.

  The content of (E) zinc dithiophosphate in the lubricating oil composition of the present invention is preferably 0.1% by mass or less, more preferably 0.08% by mass, in terms of zinc element, based on the total amount of the composition. Hereinafter, it is more preferably 0.06% by mass or less. On the other hand, the content of zinc dithiophosphate is preferably 0.01% by mass or more, more preferably 0.02% by mass or more in terms of zinc element based on the total amount of the composition. When the zinc dithiophosphate content exceeds 0.1% by mass in terms of zinc element based on the total amount of the composition, there is a concern about the effect of phosphorus and zinc on the exhaust gas purification device, and fuel consumption performance at high temperatures and On the other hand, when the content is less than 0.01% by mass, there is a possibility that the anti-wear performance is inferior, and the sulfur source in the composition is reduced and sliding. Since the production amount of molybdenum disulfide on the surface is reduced, there is a possibility that the fuel saving performance is inferior. In the present invention, the content of the component (E) is 0.01 to 0.06% by mass in terms of zinc element, based on the total amount of the composition, so that it has excellent fuel economy performance from low temperature to high temperature. This is particularly preferable because the friction characteristics of the wet clutch can be remarkably improved.

  Examples of the phosphorus compound as the component (F) of the present invention include phosphoric acid monoesters, phosphoric acid diesters, phosphoric acid triesters, phosphorous acid monoesters, phosphorous acid diesters, phosphorous acid triesters. Mention may be made of esters, thiophosphates, dithiophosphates, trithiophosphates, thiophosphites, dithiophosphites, trithiophosphites and their salts. The compounds listed here usually contain a hydrocarbon group having 2 to 30 carbon atoms, preferably 3 to 20 carbon atoms.

  Specific examples of the salt of the phosphorus compound described above include phosphoric acid monoester, phosphoric acid diester, phosphoric acid triester, phosphorous acid monoester, phosphorous acid diester, or phosphorous acid triester, and ammonia and carbon. A salt or zinc obtained by allowing a nitrogen-containing compound such as an amine compound containing only a hydrocarbon group of 1 to 20 or a hydroxyl group-containing hydrocarbon group in the molecule to act to neutralize part or all of the remaining acidic hydrogen; Examples thereof include divalent metal salts such as iron.

  One type or two or more types of these components (F) can be arbitrarily blended. In the present invention, the component (F) includes phosphoric acid monoesters, phosphoric acid diesters, phosphorous acid monoesters, phosphorous acid diesters, thiophosphoric acid esters, thiophosphorous acid esters, and salts thereof. Preferably, it is at least one selected from the group consisting of, and more preferably at least one selected from the group consisting of (sub) phosphate monoesters, (sub) phosphate diesters and salts thereof. Moreover, carbon number of the hydrocarbon group which comprises these becomes like this. Preferably it is 4-20, More preferably, it is 6-18.

  Even if the component (F) in the lubricating oil composition of the present invention is not contained, the effects of the present invention can be obtained, and further reduction in phosphorus is possible. However, in an actual vehicle test of a four-cycle engine for a motorcycle, the engine It has been confirmed that when the rotational speed is low (for example, 1,000 rpm) and high (for example, exceeding 10,000 rpm), further fuel saving effect due to the component (F) is exhibited. In some cases, the component (F) is preferably contained. The content of the component (F) is preferably 0.005% by mass or more, and more preferably 0.01% by mass or more, in terms of phosphorus element, based on the total amount of the composition. On the other hand, the component (F) is preferably 0.1% by mass or less, more preferably 0.08% by mass or less, and still more preferably 0.04% by mass in terms of phosphorus element based on the total amount of the composition. % Or less. When the content of the component (F) exceeds 0.1% by mass, not only an effect commensurate with the content cannot be obtained, but also low phosphorus cannot be formed, which is not preferable.

  The lubricating oil composition of the present invention is excellent in fuel saving performance (low friction performance) and friction characteristics of a wet clutch. For the purpose of further improving the performance, a known lubricating oil additive is added to the composition of the present invention. Can be added to the product. Examples of such additives include friction modifiers other than the component (B) of the present invention, ashless dispersants other than the component (C) of the present invention, metallic detergents other than the component (D) of the present invention, (E) component or extreme pressure additive other than component (F) and antiwear agent, antioxidant, rust inhibitor, corrosion inhibitor, viscosity index improver, pour point depressant, rubber swelling agent, antifoaming agent and coloring An agent etc. can be mentioned. These can be used alone or in combination of several kinds.

  Examples of the friction modifier other than the component (B) of the present invention include aliphatic alcohols, fatty acids, fatty acid metal salts, fatty acid esters, aliphatic amines, aliphatic amine salts, aliphatic amides, and the like. These friction modifiers are slightly inferior in fuel efficiency compared to organic molybdenum compounds. However, even if they are used in place of or in combination with the organic molybdenum compounds of the present invention, fuel efficiency and friction characteristics in wet clutches are achieved. An excellent composition can be obtained.

  As the ashless dispersant other than the component (C) of the present invention, for example, benzylamine, alkylpolyamine, polybuteneamine, modified products of these boron compounds and sulfur compounds, alkenyl succinates, and the like can be used.

  Examples of the metal detergent other than the component (D) of the present invention include alkali metal sulfonates, phenates, salicylates, alkali metal or alkaline earth metal naphthenates, and the like. Can be used in combination. Examples of the alkali metal include sodium and potassium.

  As the extreme pressure additive and antiwear agent other than the component (E) or component (F) of the present invention, for example, a sulfur compound can be used. Examples of sulfur compounds include disulfides, sulfurized olefins, and sulfurized fats and oils.

  Any antioxidant can be used as long as it is generally used in lubricating oils, such as phenol compounds and amine compounds. For example, 2,6-di-tert-butyl-4 -Alkylphenols such as methylphenol, bisphenols such as methylene-4,4-bis (2,6-di-tert-butyl-4-methylphenol), naphthylamines such as phenyl-α-naphthylamine, dialkyldiphenylamines, Phenothiazines can be used.

  As the rust inhibitor, for example, alkenyl succinic acid, alkenyl succinic acid ester, polyhydric alcohol ester, petroleum sulfonate, dinonyl naphthalene sulfonate and the like can be used.

  As the corrosion inhibitor, for example, benzotriazole, thiadiazole, and imidazole compounds can be used.

  As the viscosity index improver, a non-dispersed viscosity index improver or a dispersed viscosity index improver can be used. Specifically, a non-dispersed or dispersed polymethacrylate or olefin copolymer, or polyisobutene, polystyrene, An ethylene-propylene copolymer, a styrene-diene copolymer and a hydride thereof can be used. These weight average molecular weights are generally 5,000 to 1,000,000, but in order to further improve fuel economy performance, the weight average molecular weight is 100,000 to 1,000,000, preferably 200,000 to It is desirable to use the above viscosity index improvers which are 900,000, particularly preferably 400,000 to 800,000. In addition, when the lubricating oil composition of the present invention is used in a four-cycle engine for a motorcycle, it is particularly preferable to use a styrene-diene copolymer or a hydride thereof because it is necessary to enhance shear stability.

  As the pour point depressant, for example, a polymethacrylate polymer, an alkylated aromatic compound, a fumarate-vinyl acetate copolymer, an ethylene-vinyl acetate copolymer, and the like that are compatible with the lubricating base oil to be used can be used.

  As the antifoaming agent, for example, silicone compounds such as dimethyl silicone and fluorosilicone can be used.

  The addition amount of these additives is arbitrary, but the content of the defoaming agent is usually 0.0005 to 0.01% by mass and the content of the viscosity index improver is 0.05 to 20 based on the total amount of the composition. The content of the mass%, the corrosion inhibitor is 0.005 to 0.2 mass%, and the contents of the other additives are about 0.05 to 10 mass%, respectively.

The lubricating oil composition of the present invention not only has excellent fuel economy at medium to high temperatures and friction characteristics of wet clutches, but also has excellent performance such as anti-wear performance, high-temperature oxidation stability, cleanliness, etc. In addition, it has sufficient performance to meet the JASO motorcycle 4-cycle engine oil standard (JASO T903-2011). One of the regulations requires that the amount of sulfated ash in the composition is 1.2% by mass or less based on the total amount of the composition, but the composition of the present invention has a sulfated ash content of 1.0. A low ash type lubricating oil having a mass% or less, more preferably 0.8 mass% or less, and particularly preferably 0.7 mass% or less can be obtained. This further suppresses abnormal combustion of the engine.
Here, sulfate ash means sulfate ash measured in accordance with JIS K2272.

  Further, the lubricating oil composition of the present invention preferably has a phosphorus element content of 0.12% by mass or less based on the total amount of the composition. It is preferably 0.1% by mass or less, more preferably 0.08% by mass or less, and particularly preferably 0.07% by mass or less. As a result, adverse effects on the exhaust gas purification catalyst can be suppressed.

  Further, when the component (F) is not contained, the phosphorus element content can be reduced to 0.05% by mass or less, and a composition excellent in fuel saving performance and friction characteristics in a wet clutch can be obtained.

  When used in a four-cycle engine for motorcycles, as described in the section of (F) component, it is preferable that the (F) component is contained because further fuel saving performance can be exhibited in an actual vehicle. Such a low ash type and low phosphorus type lubricating oil composition of the present invention can greatly reduce the influence on the exhaust gas purification device, and exhaust gas purification devices such as a three-way catalyst, an oxidation catalyst, an EGR device, and a DPF. It can be advantageously used for a vehicle equipped with.

The lubricating oil composition of the present invention preferably has a kinematic viscosity at 100 ° C. of 2 mm ² / s or more, more preferably 3 mm ² / s or more. On the other hand, the kinematic viscosity at 100 ° C. is preferably 15 mm ² / s or less, more preferably 10 mm ² / s or less, further preferably 8.5 mm ² / s or less, and 7 mm ² / s or less. Even more preferably, it is most preferably 6.70 mm ² / s or less.
When the kinematic viscosity of the lubricating oil composition is less than 2 mm ² / s, not only a sufficient lubricity cannot be obtained, but the amount of evaporation is large and the oil consumption increases. Moreover, when it exceeds 15 mm < ² > / s, it will become difficult to provide fuel-saving performance.

Hereinafter, the contents of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
(Examples 1-4, Comparative Examples 1-6)
(Lubricant base oil)
Lubricating base oils were prepared by blending the base oils having the properties shown in Table 1 in the proportions shown in the upper column of Table 4.

  In addition, the 1-ring aromatic content and the aromatic content of 2 or more rings were measured by high performance liquid chromatography (HPLC) under the conditions shown in Table 2.

Additives (1) to (5) containing the following compounds were added to the lubricating base oil in the proportions shown in Table 4.
Additive (1)
(B) Molybdenum dithiocarbamate; in general formula (1), R ^{1 to} R ⁴ are alkyl groups having 8 or 13 carbon atoms, a and b are 2, and the concentration of the molybdenum element is 10.0% by mass
Additive (2)
・ (C-1) Polybutenyl succinic acid succinimide 32% by mass; nitrogen content 1.8% by mass
-(C-2) Borated polybutenyl succinimide 32% by mass; nitrogen content 1.5% by mass, boron content 1.3% by mass
-(D) Calcium sulfonate 13% by mass: Total base number 300 mgKOH / g, Ca content 12% by mass
(E-1) Zn di- (primary hexyl) dithiophosphate 1% by mass; Zn content 8.4% by mass, phosphorus content 6.6% by mass
(E-2) Zn di- (secondary hexyl) dithiophosphate 5% by mass; Zn content 8.2% by mass, phosphorus content 7.2% by mass
・ Other additives including phosphorus additives, antifoaming agents, etc. (3)
-(F) alkyl phosphate ester: phosphorus content 2.5 mass%
Additive (4)
・ Olefin copolymer (viscosity index improver)
Additive (5)
・ Alkyl methacrylate (pour point depressant)

The performance of the engine lubricating oil composition of the present invention was evaluated by the performance evaluation test shown below.
(Storage stability test)
The sample oil was placed in a high-temperature air tank maintained at 0 ° C. and 60 ° C., and the presence or absence of precipitation after one month was evaluated.

(Clutch friction characteristic evaluation)
The JASO motorcycle 4-cycle engine oil standard (JASO T903-2011) stipulates performance classifications for clutch friction characteristics in addition to physicochemical properties suitable for motorcycle 4-cycle engine oil. That is, the dynamic friction coefficient, the static friction coefficient, and the braking time were measured according to test conditions based on JASO T903-2011, and the dynamic friction characteristic index, the static friction characteristic index, and the braking time index were obtained by the following calculation methods. Next, these indexes are classified into MA1, MA2 or MB according to the following Table 3. Compositions classified as MB are low friction oils, indicating that any of the above indices are lower than the standard.

(Method of calculating dynamic friction characteristic index, etc.)
Dynamic friction characteristic index = 1 + (μd (s) −μd (B11)) / (μd (A11) −μd (B11))
μd (s): Dynamic friction coefficient of test oil μd (A11): Dynamic friction coefficient of JAFRE-A11 (high friction characteristic standard oil) μd (B11): Dynamic friction of JAFRE-B11 (low friction characteristic standard oil with friction modifier) Coefficients The static friction characteristic index and the braking time index were determined by the same calculation method, and the clutch friction characteristics were determined according to Table 3 above.

Examples 1 to 4 within the scope of the present invention are excellent in clutch friction characteristics and storage stability, but when the content of the organomolybdenum compound (B) is less than that defined in the present invention (comparison) In Example 1), the clutch friction characteristic is MA, and when it is large (Comparative Example 6), the storage stability evaluation is inferior. (A) When the viscosity at 100 ° C. of the lubricating base oil is lower than specified in the present invention (Comparative Example 2), and (A) the aromatic content of two or more rings of the lubricating base oil is the present invention. When the amount is less than the specified amount (Comparative Examples 3, 4, and 5), the storage stability is poor. In addition, when the content of the organomolybdenum compound as the component (B) is less than the amount specified in the present invention (Comparative Example 1), the result of clutch friction characteristics is MA and MB oil having low friction is not obtained.
In Table 4, mass% in the base oil column represents the composition between the base oils, and the additive in the additive column represents the composition (mass%) based on the total amount of the composition.

  The lubricating oil composition of the present invention is used for internal combustion engines such as gasoline engines, diesel engines, and gas engines, particularly for internal combustion engines equipped with exhaust gas aftertreatment devices, for drive system devices having a wet clutch, and for four-cycle engines for motorcycles. However, it can also be used for lubricating oils that require fuel-saving properties and lubricating oils that require a friction adjustment function, such as for shock absorbers.

Claims (8)

(A) A lubricant base oil having a kinematic viscosity at 100 ° C. of 2.5 to ²⁰ mm ² / s and an aromatic content of two or more rings of 0.4 mass% or more is added with (B) an organomolybdenum compound. 750-1000 mass ppm as a molybdenum element conversion amount on the basis of the total amount of the composition, (C) boron-containing succinimide and / or succinimide not containing boron, (D) alkaline earth metal detergent, (E) A lubricating oil composition containing zinc dithiophosphate.   The lubricating oil composition according to claim 1, further comprising (F) at least one phosphorus compound selected from phosphoric esters, phosphites, and salts thereof. (A) Lubricating oil composition of Claim 1 or 2 whose kinematic viscosity in 100 degreeC of lubricating oil base oil is 3-9 mm < ² > / s.   The lubrication according to any one of claims 1 to 3, wherein (C) boron-containing succinimide and / or succinimide not containing boron is contained in an amount of 0.08 to 0.3% by mass in terms of nitrogen element. Oil composition.   (D) Lubricating oil composition of any one of Claims 1-4 which contains 0.01-0.16 mass% of alkaline-earth metal type detergent by the amount of alkaline-earth metal element conversion.   (E) Lubricating oil composition of any one of Claims 1-5 which contains 0.01-0.1 mass% of zinc dithiophosphate in zinc element conversion amount.   (F) (Sub-) phosphoric acid esters contain at least one selected from phosphoric acid esters, phosphorous acid esters and salts thereof in an amount of 0.1% by mass or less in terms of phosphorus element. The lubricating oil composition according to any one of the above.   The lubricating oil composition according to any one of claims 1 to 7, wherein the sulfated ash content is 1% by mass or less.