Lubricant composition

Abstract

The lubricating oil composition of the invention comprises a lubricating base oil with a 100° C. kinematic viscosity of 1-20 mm 2 /s, and (A) a viscosity index improver having a ratio M1/M2 of 0.20 or greater, between the total area of the peaks between chemical shifts of 36-38 ppm M1 and the total area of the peaks between chemical shifts of 64-66 ppm M2, with respect to the total area of all of the peaks, in the spectrum obtained by 13 C-NMR, (B) a friction modifier, and (C) an overbased metal salt obtained by overbasing an oil-soluble metal salt with an alkaline earth metal borate.

1 . A lubricating oil composition comprising:
 a lubricating base oil with a 100° C. kinematic viscosity of 1-20 mm 2 /s,   a viscosity index improver having a ratio M1/M2 of 0.20 or greater, between the total area of the peaks between chemical shifts of 36-38 ppm M1 and the total area of the peaks between chemical shifts of 64-66 ppm M2, with respect to the total area of all of the peaks, in the spectrum obtained by  13 C-NMR,   a friction modifier, and   an overbased metal salt obtained by overbasing an oil-soluble metal salt with an alkaline earth metal borate.   
     
     
         2 . A lubricating oil composition according to  claim 1 , wherein the viscosity index improver is a poly(meth)acrylate-based viscosity index improver. 
     
     
         3 . A lubricating oil composition according to  claim 1 , wherein the second viscosity index improver has a PSSI of no greater than 40 and a weight-average molecular weight/PSSI ratio of at least 1×10 4 . 
     
     
         4 . A lubricating oil composition according to  claim 1 , wherein the friction modifier is an organic molybdenum compound. 
     
     
         5 . A lubricating oil composition according to  claim 1 , wherein the overbased metal salt obtained by overbasing the oil-soluble metal salt with the alkaline earth metal borate is an alkaline earth metal salicylate obtained by overbasing an alkaline earth metal salicylate with an alkaline earth metal borate.