| 摘要 |
PURPOSE:To obtain the subject new lubricating oil composition having an improved oil film thickness in a condition of elastic fluid lubrication by blending a specified amount of a polymer-based viscosity index improver with a specified naphthene-based base oil and adjusting its viscosity to a specified value. CONSTITUTION:With (A) a naphthene-based base oil, >=80wt.% in sum of the amount of carbons constituting the condensed polycyclic aliphatic hydrocarbon and those directly bonded to the constituting carbon, based on the whole carbons, and having 1.65-1.80H/C ratio and 0.98-1.20g/cm<3> density (at 15 deg.C) is blended (B) 0.2-10wt.% polymer-based viscosity index improver composed of a poly(meth)acrylate, polyisobutylene, ethylene/propylene copolymer, or a styrene/maleic anhydride copolymer, etc., having 1000-100000 molecular weight, thus obtaining the objective composition having 100-400cSt viscosity at 40 deg.C. |
