| abstract |
An object is to provide a viscosity index improver composition that is capable of properly regulating the HTHS viscosity in the effective temperature range of a lubricating oil composition to a lower range, and a lubricating oil composition containing the viscosity index improver composition, and the viscosity index improver composition contains a comb-shaped polymer (A) containing a structural unit derived from a macromonomer (α) and a structural unit derived from a particular monomer (A1), the macromonomer (α) having a (meth)acryloyl group at one end, and having a structural unit derived from a monomer (α1) selected from butadiene and hydrogenated butadiene. |