| abstract |
Lubricating oil composition comprising: a lubricating base oil including a lubricating base oil component having a kinematic viscosity of 1 to 10 mm2 / s at 100 ° C and a% CA of 5 or less, where the amount of the oil component lubricating base is 30% by mass or higher based on the total mass of the lubricating base oil; and a viscosity index improver having a weight average molecular weight of 50,000 or greater and a ratio of the weight average molecular weight to the IECP of 1.0 x 104 or greater, where the amount of the viscosity index improver is about 0.1 to 50% by mass based on the total mass of the lubricating oil composition, where the viscosity index improver contains one or more (meth) acrylate structural units represented by the following general formula (1) ** Formula ** where R1 represents hydrogen or a methyl group and R2 represents a linear or branched hydrocarbon group of 16 or more carbon atoms, and where the proportion of the structural unit represented by the general formula (1) is from 1 to 70% in moles, the composition of the lubricating oil having a kinematic viscosity of 3 to 9.3 mm2 / s at 100 ° C and a ratio between the ATAC viscosity at 150 ° C and the ATAC viscosity at 100 ° C of 0.52 or higher, where the IECP is the index of permanent shear stability that complies with ASTM B 6022-01 and is calculated according to ASTM D 6278-02, and where the ATAC viscosity is the high temperature and high shear viscosity measured according to ASTM D 4683. |