| abstract |
(57) [Problem] To provide a viscosity index improver which is excellent in shear stability and has good economic efficiency to give a lubricating oil composition, and a lubricating oil composition containing the viscosity index improver. The viscosity index improver for lubricating oil has 2 carbon atoms. A polymer of at least one α-olefin selected from α-olefins having a number average molecular weight of 20, It is composed of an olefin polymer having an Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) of 1.5 to 2,000 to 2,000,000. The lubricating oil composition contains the above-mentioned viscosity index improver for lubricating oil, a lubricating oil base material, and if necessary, a pour point depressant. |