| 摘要 |
PROBLEM TO BE SOLVED: To provide a viscosity index improver which can sufficiently decrease a high shear viscosity at 100°C while maintaining a high shear viscosity at 150°C and exhibits a high shear stability, and to provide a lubrication oil additive and a lubricating oil composition containing the viscosity index improver.SOLUTION: There is provided a poly(meth)acrylate-based viscosity index improver which has a core and three or more arms which are composed of a polymer chain containing a structural unit represented by the following general formula (1) and in which one end of the polymer chain is bonded to the core. The weight average molecular weight (Mw) of the poly(meth)acrylate-based viscosity index improver is 100000 or more and the ratio (Mw/Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 1.6 or less. |
