Lubricating-oil composition

Abstract

The lubricating oil composition of the present invention comprises a base oil that contains at least one selected from the group consisting of a mineral oil and a synthetic oil, has a viscosity index of 120 or more, and has a paraffin content by ring analysis of 70% or more; a dispersant (A) containing one or more compounds selected from the group consisting of an alkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimide and a boronated alkylsuccinimide; and a molybdenum dithiocarbamate (B); wherein the component (A) is contained in an amount of from 0.01% by mass to 0.10% by mass in terms of the nitrogen content thereof based on the total amount of the composition, one or more compounds selected from the group consisting of a boronated alkenylsuccinimide and a boronated alkylsuccinimide in the component (A) are contained in an amount of from 0.05% by mass to 3.5% by mass based on the total amount of the composition, the phosphorus content is from 100 ppm by mass to 1200 ppm by mass, the sulfated ash content is 1.2% by mass or less, and the molybdenum content is from 300 ppm by mass to 1000 ppm by mass. Accordingly, even when used in automobile internal combustion engines capable of increasing the thermal and mechanical durability temperature thereof more than before and capable of realizing power increase and fuel efficiency, the lubricating oil composition can prevent engine performance degradation and therefore can satisfy both the requirements of engine performance and engine durability.

1 . A lubricating oil composition comprising:
 a base oil that contains at least one selected from the group consisting of a mineral oil and a synthetic oil, has a viscosity index of 120 or more, and has a paraffin content by ring analysis of 70% or more;   (A) a dispersant containing one or more compounds selected from the group consisting of an alkenylsuccinimide, a boronated alkenylsuccinimide, an alkylsuccinimide and a boronated alkylsuccinimide; and   (B) a molybdenum dithiocarbamate;   wherein   the component (A) is contained in an amount of from 0.01% by mass to 0.10% by mass in terms of the nitrogen content thereof based on the total amount of the composition,   one or more compounds selected from the group consisting of a boronated alkenylsuccinimide and a boronated alkylsuccinimide in the component (A) are contained in an amount of from 0.05% by mass to 3.5% by mass based on the total amount of the composition,   the phosphorus content based on the total amount of the composition is from 100 ppm by mass to 1200 ppm by mass,   the sulfated ash content based on the total amount of the composition is 1.2% by mass or less, and   the molybdenum content based on the total amount of the composition is from 300 ppm by mass to 1000 ppm by mass.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the component (A) contains a boron compound, and the ratio by mass of boron to nitrogen, B/N ratio in the component (A) is 0.5 or more. 
     
     
         3 . The lubricating oil composition according to  claim 1 , comprising an antioxidant selected from the group consisting of an amine-based antioxidant, a phenol-based antioxidant and a molybdenumamine-based antioxidant, in an amount of from 0.3% by mass to 3% by mass based on the total amount of the lubricating oil composition. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the phosphorus content is from 200 ppm by mass to 1100 ppm by mass. 
     
     
         5 . The lubricating oil composition according to  claim 2 , wherein the B/N ratio is 0.6 or more. 
     
     
         6 . The lubricating oil composition according to  claim 1 , which is used for lubrication in internal combustion engines. 
     
     
         7 . The lubricating oil composition according to  claim 6 , which is used for lubrication in internal combustion engines where at least a piston head thereof is formed of a cast iron material.