JP4733974B2 - Lubricating oil composition - Google Patents

Description

  The present invention relates to a low-friction lubricating oil particularly useful for lubricating various engines (internal combustion engines) such as diesel engines, gasoline engines, engines using liquid fuel such as dimethyl ether, and gas engines using gaseous fuel. Relates to the composition.

  Low friction is a characteristic required for lubricating oil compositions, particularly lubricating oils for automobile engines called engine oils. That is, in order to prevent energy loss due to friction in the engine during driving of an automobile, there is a demand for imparting low friction as an improvement on the lubricating oil side.

  In Patent Document 1, as a lubricating oil composition excellent in reducing mechanical friction loss of a 4-cycle engine, sulfur oxide oxymolybdenum organophosphorodithioate and / or molybdenum dithiocarbamate is added to a base oil made of mineral oil or synthetic oil. 2-5% by mass, 0.1-7% by mass of zinc dithiophosphate having a specific chemical composition, 0.1-20% by mass of calcium alkylbenzenesulfonate, and alkenyl succinimide and / or alkenyl succinimide There is a description of a lubricating oil composition comprising 1 to 15% by mass of a boron compound derivative. In Patent Document 1, sulfurized oxymolybdenum organophosphorodithioate and / or molybdenum dithiocarbamate acts as an extreme pressure agent, and if the addition amount is less than 0.2% by mass, a sufficient addition effect does not appear. It is described.

In Patent Document 2, as an engine oil, an oxymolybdenum complex and a sulfurized oxymolybdenum dithiocarbamate (provided as a reaction product of 0.045% by mass or more of an acidic molybdenum compound and a basic nitrogen compound in terms of the total molybdenum content) There is a description of using a composition containing the latter sulfur oxymolybdenum dithiocarbamate content of less than 0.0175% by mass in terms of molybdenum content.
Japanese Patent Publication No. 3-23595 US Pat. No. 6,562,765 B1 specification

  As described above, a technique for increasing the friction reduction effect by adding a molybdenum-containing organic compound to a lubricating oil composition used as an engine oil is already known. However, the following points must be taken into account for the addition of molybdenum-containing organic compounds to the lubricating oil composition.

1) When a large amount of an organic compound containing molybdenum is added, the total metal content in the lubricating oil composition increases, and it is difficult to satisfy the demand for a lubricating oil composition having a low sulfated ash content in recent years.
2) When a large amount of molybdenum-containing organic compound (particularly sulfurized oxymolybdenum dithiocarbamate) is added, the lubricating oil composition tends to become corrosive or increase the generation of sludge (deteriorated deposits).
3) Molybdenum-containing organic compounds are not easy to synthesize, and the cost required for raw materials and production is high. Therefore, the use of a large amount reduces the economic efficiency as a lubricating oil composition.
4) As described in Patent Document 1, when a small amount of molybdenum-containing organic compound is used, the friction reducing effect is hardly exhibited.

  An object of the present invention is to provide a lubricating oil composition exhibiting a high friction reducing effect while suppressing the amount of molybdenum-containing organic compound used.

The present invention resides in an engine lubricating oil composition in which the following components are dissolved or dispersed in a lubricating base oil in the following amounts based on the total amount of the lubricating oil composition.
a) 0.01 to 0.3% by mass of a nitrogen-containing ashless dispersant in terms of nitrogen content;
b) 0.05 to 0.5% by mass of a metal-containing detergent in terms of metal content;
c) 0.01 to 0.12% by mass of zinc dihydrocarbyl dithiophosphate or zinc dihydrocarbyl phosphate in terms of phosphorus content;
d) Molybdenum compound containing 0.04 to 0.19 mass% of the following two kinds of compounds in terms of molybdenum content,
d ₁ ) an oxymolybdenum complex which is a reaction product of 0.02 to 0.15% by mass of an acidic molybdenum compound and succinimide in terms of molybdenum content,
d ₂ ) 0.02 to 0.15 mass% of sulfurized oxymolybdenum dithiocarbamate in terms of molybdenum content ;
And e) 0.1 to 3 wt% polyhydric alcohol mono-fatty acid ester le of boric oxide.

  Even when a small amount of molybdenum-containing organic compound is added, a lubricating oil composition exhibiting a high friction reducing effect can be obtained.

Preferred embodiments of the invention will now be described.
(1) The lubricating base oil has a kinematic viscosity at 100 ° C. in the range of ² to 6 mm ² / s, and A
A base oil with an evaporation loss of 17% by weight or less according to STM D5800.
(2) The nitrogen-containing ashless dispersant contains a bis-type succinimide reacted with boric acid and / or a bis-type succinimide reacted with a cyclic carbonate.
(3) The metal-containing detergent has salicylate, carboxylate, or sulfonate as a main component.
(4) The total content of the molybdenum compound is in the range of 0.04 to 0.15 mass% in terms of molybdenum content, and both the content of the compounds d ₁ and d ₂ are in terms of molybdenum content. In the range of 0.02 to 0.10% by mass.
(5) content of the polyhydric alcohol mono-fatty acid ester le of boric oxide is in the range of 0.2 to 1 wt%.
(6) Furthermore, the organic antioxidant of 1 type or 2 or more types chosen from the group which consists of 0.01 to 5weight% of a phenolic compound and an amine compound is included.
(7) The lubricating oil composition is for lubricating a gasoline engine or a diesel engine. (8) The viscosity of the lubricating oil composition is SAE viscosity grade and is 0W20, 0W30, 5W20 or 5W30.

  The composition of the lubricating oil composition of the present invention will be described in more detail.

As the lubricating base oil in the lubricating oil composition of the present invention, a base oil (mineral oil, synthetic oil or those having a kinematic viscosity in the range of ² to 6 mm ² / s and having an evaporation loss of 17% by mass or less according to ASTM D5800. It is preferable to use a mixture of There are no particular restrictions on the type of mineral oil or synthetic oil, or other properties, but the sulfur content is preferably 0.1% by mass or less, more preferably 0.03% by mass or less, especially It is desirable that it is 0.005 mass% or less.

  It is desirable that the mineral oil-based base oil is obtained by processing a mineral oil-based lubricating oil fraction by appropriately combining processing methods such as solvent refining or hydrotreating, and particularly a highly hydrorefining (hydrocracking) group. Oil (for example, a base oil having a viscosity index of 100 to 150, an aromatic content of 5% by mass or less, and nitrogen and sulfur contents of 50 ppm or less) is preferably used. This includes high-viscosity index base oils produced by isomerization and hydrocracking processes using mineral oil-based slack wax (rough wax) or synthetic wax synthesized from natural gas as a raw material. Hydrocracked base oils are preferred from the standpoints of low sulfur content, low evaporability, and low residual carbon content. The most preferred lubricating base oil is a mineral oil having an evaporation loss (ASTM D5800) of 15% by mass or less, a saturated component of 90% by mass or more, an aromatic component of 10% by mass or less, and a sulfur content of 0.01% by mass or less. Or a base oil mixture containing 10% by mass or more of the mineral oil.

  Synthetic oils (synthetic lubricating base oils) include, for example, poly-α-olefins which are polymers of α-olefins having 3 to 12 carbon atoms, sebacic acid, azelaic acid, adipic acid represented by dioctyl sebacate, etc. Dialkyl diester which is an ester of a dibasic acid and an alcohol having 4 to 18 carbon atoms, polyol ester which is an ester of 1-trimethylolpropane or pentaerythritol and a monobasic acid having 3 to 18 carbon atoms, 9 to 40 carbon atoms And alkylbenzene having an alkyl group of

  Mineral base oils and synthetic base oils can be used alone, but if desired, two or more mineral base oils or a combination of two or more synthetic base oils may be used. it can. Further, if desired, a mineral base oil and a synthetic base oil can be used in combination at any ratio.

  Examples of the nitrogen-containing ashless dispersant (that is, the nitrogen element-containing ashless dispersant) as the component a) in the lubricating oil composition of the present invention include alkenyl or alkyl succinimides derived from polyolefins or derivatives thereof. Preferably used. Exemplary succinimides include succinic anhydrides substituted with high molecular weight alkenyl or alkyl groups and polyalkylene polyamines containing an average of 4 to 10 (preferably 5 to 7) nitrogen atoms per molecule; It can obtain by reaction of. The high molecular weight alkenyl or alkyl group is preferably a polybutene having a number average molecular weight of about 900 to 5,000.

  In the step of obtaining polybutenyl succinic anhydride by reaction of polybutene and maleic anhydride, a chlorination method using chlorine is often used. However, this method results in a large amount of chlorine (eg, about 2000 ppm by weight) remaining in the succinimide final product. On the other hand, in the thermal reaction method using no chlorine, chlorine remaining in the final product can be kept at a very low level (for example, 0 to 30 ppm by mass). Therefore, in order to suppress the chlorine content in the lubricating oil composition to an amount in the range of 0 to 30 ppm by mass, it is necessary to use succinimide from polybutenyl succinic anhydride obtained by a thermal reaction method. desirable. The succinimide can be used as a so-called modified succinimide by further reacting with boric acid, alcohol, aldehyde, ketone, alkylphenol, cyclic carbonate (eg, ethylene carbonate), organic acid or the like. In particular, boron-containing alkenyl (or alkyl) succinimide obtained by reaction with boric acid or a boron compound is advantageous in terms of thermal and oxidation stability. In addition, the succinimide dispersant includes a polymeric succinimide dispersant derived from an ethylene / α-olefin copolymer (for example, a molecular weight of about 1000 to 15000), which is also preferably used.

  The lubricating oil composition of the present invention preferably contains an alkenyl or alkyl succinimide or a derivative thereof, or a nitrogen-containing ashless dispersant such as alkenyl benzylamine as an essential component. A nitrogen-free ashless dispersant may also be used in combination.

  The metal-containing detergent that is the component b) in the lubricating oil composition of the present invention (that is, also referred to as a metal element-containing detergent or metal detergent) has a sulfur content of 3.5% or less and a total base number of 10 to 10. It is desirable to use 400 mg KOH / g of a metal-containing detergent in a range of 0.1 to 1.5% by mass in terms of sulfated ash.

  As the metal-containing detergent, sulfurized phenate (eg, calcium sulfide phenate), petroleum or synthetic sulfonate (eg, calcium sulfonate), phenoxysulfonate, salicylate (eg, calcium salicylate) or carboxylate can be used. Preference is given to salicylates, carboxylates and sulfonates. The metal-containing detergent is preferably one containing boron (boric acid treated product).

  The zinc dihydrocarbyl dithiophosphate, which is the component c) of the lubricating oil composition of the present invention, is usually a primary alkyl group or a secondary alkyl group type zinc dialkyl dithiophosphate. Among zinc dialkyldithiophosphates, zinc dialkyldithiophosphates containing secondary alkyl groups derived from secondary alcohols having 3 to 18 carbon atoms are advantageous because of their high anti-wear performance. . On the other hand, zinc dialkyldithiophosphates containing primary alkyl groups derived from primary alcohols having 3 to 18 carbon atoms are known to have high heat resistance and excellent friction reduction. Therefore, these various zinc dialkyldithiophosphates can be used alone or in combination depending on the purpose. In view of friction reduction, which is an object of the present invention, a composition mainly composed of zinc dialkyldithiophosphate containing a primary alkyl group is preferred.

  A mixed type zinc dialkyldithiophosphate having a primary alkyl group and a secondary alkyl group derived from a mixed alcohol of a primary alcohol and a secondary alcohol can also be used.

If necessary, zinc dialkylaryl dithiophosphate (eg, zinc dialkylarylthiodiphosphate derived from dodecylphenol) is also effectively used.
Further, zinc dihydrocarbyl phosphate containing no sulfur atom may be used instead of zinc dihydrocarbyl dithiophosphate.

The lubricating oil composition of the present invention, as a friction reducing agent (friction modifier), by using a combination of boric oxide with a small amount of molybdenum-containing compounds and polyhydric alcohol fatty acid monoester, low metal content as a whole Excellent friction reduction effect in quantity. However, as the molybdenum-containing compound, an oxymolybdenum complex which is a reaction product of an acidic molybdenum compound and succinimide is used in combination with sulfurized oxymolybdenum dithiocarbamate.

The oxymolybdenum complex, which is a reaction product of an acidic molybdenum compound and succinimide, has a detailed description in Patent Document 2 described above. The oxymolybdenum complex can be used as it is, but it is preferable to use a reaction product obtained by reacting with a small amount of sulfur or a sulfur compound. Such a reaction product containing sulfur is also described in Patent Document 2 described above. In particular, low-temperature sulfidation of oxymolybdenum complexes using this foil imide is preferably used. However, from the viewpoint of reducing the sulfur content of the lubricating oil composition, those having a low sulfur content are preferred, and the sulfur content is preferably 10% by mass or less of the molybdenum content (Mo content).

For the sulfurized oxymolybdenum dithiocarbamate Mae bets is described in detail in Patent Document 1 above.

  As the molybdenum-containing compound, a molybdenum-containing compound such as oxymolybdenum monoglyceride, oxymolybdenum diethylate amide, or amine molybdenum complex compound can be used in combination.

  The polyhydric alcohol monofatty acid borate used in the lubricating oil composition of the present invention is also a known compound as a friction reducing agent, and examples thereof include glycerin monooleate borate. . The borate of the polyhydric alcohol mono fatty acid ester is described in detail in JP-A-59-25891.

  The lubricating oil composition of the present invention further contains 0.01 to 5 mass% (preferably 0.1 to 3 mass%) of an antioxidant phenolic compound and / or an antioxidant amine compound as an antioxidant. It is preferable to include in the range. Such an antioxidant is preferably a diarylamine antioxidant and / or a hindered phenol antioxidant. These antioxidants are also effective in improving high temperature cleanability. In particular, diarylamine-based antioxidants are advantageous in this respect because they have a base number derived from nitrogen. The hindered phenol antioxidant is advantageous in preventing NOx oxidation deterioration.

  Examples of hindered phenol antioxidants include 2,6-di-t-butyl-p-cresol, 4,4′-methylenebis (2,6-di-t-butylphenol), 4,4′-methylenebis ( 6-t-butyl-o-cresol), 4,4′-isopropylidenebis (2,6-di-t-butylphenol), 4,4′-bis (2,6-di-t-butylphenol), 2 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 4,4'-thiobis (2-methyl-6-tert-butylphenol), 2,2-thio-diethylenebis [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate], and octyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 3- (3,5-di-t-butyl) -4-hi Rokishifeniru) can be mentioned hindered phenols such as acetic acid and propionic acid octadecyl.

  Examples of diarylamine antioxidants include mixed alkyl diphenylamines having 4 to 9 carbon atoms, p, p′-dioctyldiphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, alkylated-α-naphthylamine, and Mention may be made of diarylamines such as alkylated-phenyl-α-naphthylamine. The hindered phenol antioxidant and the diarylamine antioxidant can be used alone or in combination as desired. Moreover, you may use together oil-soluble antioxidant other than these.

  The lubricating oil composition of the present invention preferably further contains a viscosity index improver in an amount of 20% by mass or less (preferably in the range of 1 to 20% by mass). Examples of the viscosity index improver include polymer compounds such as polyalkyl methacrylate, ethylene-propylene copolymer, styrene-butadiene copolymer, and polyisoprene. Alternatively, a dispersion-type viscosity index improver or a multifunctional viscosity index improver that imparts dispersion performance to these polymer compounds can be used. These viscosity index improvers can be used alone, but any viscosity index improver may be used in combination of two or more.

  The lubricating oil composition of the present invention may further contain various auxiliary additives. Examples of such auxiliary additives include, as antioxidants or antiwear agents, zinc dithiocarbamate, methylenebis (dibutyldithiocarbamate), oil-soluble copper compounds, sulfur compounds (eg, sulfurized olefins, sulfurized esters, Polysulfide), phosphate ester, phosphite ester, organic amide compound (eg, oleylamide) and the like. In addition, compounds such as benzotriazole compounds and thiadiazole compounds that function as metal deactivators can be added. In addition, polyoxyalkylene nonionic surfactants such as polyoxyethylene alkylphenyl ethers functioning as rust inhibitors or demulsifiers and copolymers of ethylene oxide and propylene oxide can also be added. Various amines, amides, amine salts and derivatives thereof that function as friction modifiers, fatty acid esters of polyhydric alcohols, or derivatives thereof can also be added. Furthermore, various compounds that function as an antifoaming agent or a pour point depressant can also be added. These auxiliary additives are preferably used in an amount of 3% by mass or less (particularly in the range of 0.001 to 3% by mass) with respect to the lubricating oil composition.

(1) Production of Lubricating Oil Composition A lubricating oil composition according to the present invention and a comparative lubricating oil composition were produced using the following additive components and base oil. These lubricating oil compositions were prepared to show 0W20 in SAE viscosity grade with the addition of viscosity index improvers.

(2) Additives and base oil Ashless dispersant A: Ethylene carbonate reaction-treated succinimide dispersant [nitrogen content: 1.0 mass%, chlorine content: 30 mass ppm, polybutene having a number average molecular weight of about 2300 (at least 50% The above was prepared from a maleic anhydride and a maleic anhydride, and then reacted with a polyalkylene polyamine having an average number of nitrogen atoms of 6.5 (per molecule), and then obtained. Reaction of bis-succinimide with ethylene carbonate]

  Ashless dispersant B: Boron-containing succinimide dispersant [nitrogen content: 1.95 mass%, boron content: 0.66 mass%, chlorine content: less than 5 mass ppm, polybutene having a number average molecular weight of about 1300 (at least 50 % Having a methylvinylidene structure) and maleic anhydride by a thermal reaction method, reacting it with a polyalkylene polyamine having an average nitrogen atom number of 6.5 (per molecule), and then obtaining the bis Type succinimide reacted with boric acid]

  Metal-containing detergent: calcium salicylate (Ca: 6.7% by mass, S: 0.1% by mass, B: 2.7% by mass, TBN: 190 mg KOH / g), calcium salt of alkyl salicylic acid with calcium borate Basified.

  Zinc dihydrocarbyl dithiophosphate (ZnDTP) -1: zinc dialkyldithiophosphate (P: 7.2% by mass, Zn: 7.85% by mass, S: 14% by mass, secondary material having 3 to 8 carbon atoms as a raw material Manufactured using alcohol)

  Zinc dihydrocarbyl dithiophosphate (ZnDTP) -2: zinc dialkyldithiophosphate (P: 7.3 mass%, Zn: 8.4 mass%, S: 14 mass%, primary alcohol having 8 carbon atoms as a raw material) Manufactured using)

  Oxymolybdenum complex (OLOA17502 manufactured by Chevron Texaco Japan Co., Ltd., Mo: 5.5% by mass, S: 0.2% by mass, N: 1.6% by mass, TBN: 10 mgKOH / g, sulfur-containing oxymolybdenum・ Succinimide complex)

Molybdenum dithiocarbamate (Sakuralube 165 manufactured by Asahi Denka Kogyo Co., Ltd., Mo: 4.5% by mass, S: 4.7% by mass, sulfurized oxymolybdenum dithiocarbamate, alkyl group is C ₈ and C ₁₃ primary alkyl Group mixing)

  A borate of a polyhydric alcohol monofatty acid ester (borate of a monooleic acid ester of glycerol, B: 2.2% by mass).

Amine-based antioxidant [dialkyldiphenylamine (alkyl group: mixture of C ₄ and C ₈ ), N: 4.6% by mass, TBN: 180 mgKOH / g]

  Viscosity index improver (VII): Dispersed polymethacrylate compound

  Pour point depressant (PPD): Polymethacrylate compound

Base oil: hydrocracked base oil (kinematic viscosity at 100 ° C. is 4.1 mm ² / s, viscosity index is 127, evaporation loss (ASTM D5800) is 15% by mass, sulfur content is less than 0.001% by mass, (Saturated component is 94% by mass, aromatic content is 6% by mass)

[Example 1]
(1) The lubricant composition of the present invention was prepared by adding and mixing the following components (addition amount based on the total amount of the lubricating oil composition) to the base oil.

Ashless dispersant A (addition amount: 1.0 mass%, addition amount in terms of nitrogen: 0.01 mass%)
Ashless dispersant B (addition amount: 2.6% by mass, addition amount in terms of nitrogen amount: 0.05% by mass)
Metal-containing detergent (addition amount: 3.0% by mass, addition amount in terms of calcium: 0.2% by mass)
ZnDTP-1 (addition amount: 0.28 mass%, phosphorus content conversion addition amount: 0.02 mass%)
ZnDTP-2 (addition amount: 0.68 mass%, phosphorus content conversion addition amount: 0.05 mass%)
Oxymolybdenum complex (addition amount: 0.73 mass%, molybdenum conversion addition amount: 0.04 mass%)
Molybdenum dithiocarbamate (addition amount: 1.1 mass%, molybdenum conversion addition amount: 0.05 mass%)
Borate of polyhydric alcohol mono fatty acid ester (0.4% by mass)
Amine-based antioxidant (addition amount: 0.9% by mass)
VII (addition amount: 7.9% by mass)
PPD (added amount: 0.3% by mass)
Base oil (remaining amount)

(2) The chemical characteristics of the resulting lubricating oil composition are described below.
Phosphorus (P) content: 0.07% by mass
Sulfur (S) amount: 0.23 mass%
Calcium (Ca) content: 0.3% by mass
Chlorine (Cl) content: less than 5 mass ppm

[Comparative Example 1]
A lubricating oil composition having the same composition as in Example 1 was prepared except that the oxymolybdenum complex, molybdenum dithiocarbamate, and borate of a polyhydric alcohol fatty acid ester were not added.

[Comparative Example 2]
A lubricating oil composition having the same composition as in Example 1 was prepared except that molybdenum dithiocarbamate and a borate of a polyhydric alcohol fatty acid ester were not added.

[Comparative Example 3]
A lubricating oil composition having the same composition as in Example 1 was prepared, except that the amount of molybdenum dithiocarbamate added was 0.011% by mass in terms of molybdenum, and the borate of the polyhydric alcohol was not added.

[Comparative Example 4]
A lubricating oil composition having the same composition as Example 1 was prepared except that the oxymolybdenum complex was not added.

[Performance evaluation of lubricating oil composition]
(1) Motor ring torque test Test including engine head, electric motor, oil pump, temperature control device, and rotational torque measuring instrument including OHC valve system (including slip type cam and follower) of a 4-cylinder gasoline engine. Using a machine, the rotation speed was changed at an oil temperature of 100 ° C., and the rotational torque (friction) was measured. This measurement measures the friction across both fluid and boundary lubrication.

(2) Results of rotational torque measurement are shown in Table 1 below. The unit of rotational torque is kgm.

Table 1
────────────────────────────────────
Rotational speed (rpm)
Test oil 375 500 750 1000
────────────────────────────────────
Example 1 0.362 0.299 0.288 0.272
────────────────────────────────────
Comparative Example 1 0.668 0.581 0.470 0.406
Comparative Example 2 0.663 0.579 0.472 0.403
Comparative Example 3 0.590 0.516 0.438 0.400
Comparative Example 4 0.443 0.377 0.347 0.332
────────────────────────────────────

(3) Conclusion From the above measurement results, the friction reducing effect is obtained by adding a small amount of two kinds of molybdenum compounds and polyhydric alcohol monofatty acid ester (or its borate) in addition to the basic composition of the lubricating oil composition. It is clear that an excellent lubricating oil composition is obtained.

Claims (8)

An engine lubricating oil composition in which the following components are dissolved or dispersed in a lubricating base oil in the following amounts based on the total amount of the lubricating oil composition:
a) 0.01 to 0.3% by mass of a nitrogen-containing ashless dispersant in terms of nitrogen content;
b) 0.05 to 0.5% by mass of a metal-containing detergent in terms of metal content;
c) 0.01 to 0.12% by mass of zinc dihydrocarbyl dithiophosphate or zinc dihydrocarbyl phosphate in terms of phosphorus content;
d) Molybdenum compound containing 0.04 to 0.19 mass% of the following two kinds of compounds in terms of molybdenum content,
d ₁ ) an oxymolybdenum complex which is a reaction product of 0.02 to 0.15% by mass of an acidic molybdenum compound and succinimide in terms of molybdenum content,
d ₂ ) 0.02 to 0.15 mass% of sulfurized oxymolybdenum dithiocarbamate in terms of molybdenum content ;
And e) 0.1 to 3 wt% polyhydric alcohol mono-fatty acid ester le of boric oxide. The lubricating oil composition according to claim 1, wherein the lubricating base oil is a base oil having a kinematic viscosity at 100 ° C. in the range of ² to 6 mm ² / s and an evaporation loss of 17% by mass or less according to ASTM D5800.   The lubricating oil composition according to claim 1, wherein the nitrogen-containing ashless dispersant includes a bis-type succinimide reacted with boric acid and / or a bis-type succinimide reacted with a cyclic carbonate.   The lubricating oil composition according to claim 1, wherein the metal-containing detergent contains salicylate, carboxylate, or sulfonate as a main component. The total content of the molybdenum compounds is in the range of 0.04 to 0.15% by mass in terms of molybdenum content, and both the d ₁ and d ₂ compounds content is 0.00 in terms of molybdenum content. The lubricating oil composition according to claim 1, which is in the range of 02 to 0.10 mass%. The lubricating oil composition of claim 1 in which the content of the polyhydric alcohol mono-fatty acid ester le of boric oxide is in the range of 0.2 to 1 wt%.   The lubricating oil composition according to claim 1, further comprising one or more organic antioxidants selected from the group consisting of 0.01 to 5% by weight of a phenol compound and an amine compound.   The lubricating oil composition according to claim 1, which is used for lubricating a gasoline engine or a diesel engine.