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 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 having a polymer chain containing a structural unit represented by the following general formula (1), where the weight average molecular weight 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. |