Lubricating oil composition for internal combustion engines

Abstract

Provided is a lubricant oil composition for an internal combustion engine which is characterized by including a base oil having a viscosity index of 125 or higher and a Noack evaporation amount (250° C.×1 h) of 15% by mass or less, and, based on a total amount of the composition, from 0.1 to 10% by mass of (A) a C 2 to C 20 olefin polymer having a mass average molecular weight of 500 or more and 10,000 or less and/or (B) a polymeric compound having a mass average molecular weight of 10,000 or more and less than 100,000, wherein a content of (C) a polymeric compound having a mass average molecular weight of 100,000 or more is less than 1.0% by mass. The lubricant oil composition can, despite of its low viscosity, reduce noise during running, prevent fatigue damage such as gear pitting, reduce the consumption of the oil, and provide excellent fuel saving performance.

1 . A lubricant oil composition, comprising:
 a base oil having a viscosity index of 125 or higher and a Noack evaporation amount (250° C.×1 h) of 15% by mass or less; and   from 0.1 to 10% by mass, based on a total amount of the composition, of
 (A) a C 2  to C 20  olefin polymer having a mass average molecular weight of 500 or more and 10,000 or less, 
 (B) a polymeric compound having a mass average molecular weight of 10,000 or more and less than 100,000, or 
 (A) and (B), 
   
       wherein a content of (C) a polymeric compound having a mass average molecular weight of 100,000 or more is less than 1.0% by mass. 
     
     
         2 . The composition of  claim 1 , comprising at least one polymeric compound (B) selected from the group consisting of a polymethacrylate, an olefin copolymer, a styrene copolymer, and a polyisobutylene. 
     
     
         3 . The composition of for  claim 1 , further comprising a molybdenum-based friction modifier or an ashless friction modifier. 
     
     
         4 . The composition of  claim 1 , wherein the Noack evaporation amount (250° C.×1 h) of the base oil is 10.0% by mass or less and the viscosity index of the base oil is 140 or higher. 
     
     
         5 . The composition of  claim 1 , which is suitable for a four-cycle engine in a motorcycle. 
     
     
         6 . The composition of  claim 1 , wherein the polymeric compound (C) is at least one selected from the group consisting of a polymethacrylate, an olefin copolymer, a styrene copolymer, and a polyisobutylene. 
     
     
         7 . The composition of  claim 1 , comprising the C 2  to C 20  olefin polymer (A). 
     
     
         8 . The composition of  claim 1 , comprising the polymeric compound (B). 
     
     
         9 . The composition of  claim 1 , comprising the C 2  to C 20  olefin polymer (A) and the polymeric compound (B). 
     
     
         10 . The composition of  claim 2 , further comprising a molybdenum-based friction modifier or an ashless friction modifier. 
     
     
         11 . The composition of  claim 3 , comprising the molybdenum-based friction modifier. 
     
     
         12 . The composition of  claim 3 , comprising the ashless friction modifier. 
     
     
         13 . The composition of  claim 10 , comprising the molybdenum-based friction modifier. 
     
     
         14 . The composition of  claim 10 , comprising the ashless friction modifier. 
     
     
         15 . The composition of  claim 2 , wherein the Noack evaporation amount (250° C.×1 h) of the base oil is 10.0% by mass or less and the viscosity index of the base oil is 140 or higher. 
     
     
         16 . The composition of  claim 3 , wherein the Noack evaporation amount (250° C.×1 h) of the base oil is 10.0% by mass or less and the viscosity index of the base oil is 140 or higher.