Engine oil composition

Abstract

An engine oil composition comprising: a lubricating base oil having a kinematic viscosity at 100° C. of 1 to 5 mm 2 /s; a poly(meth)acrylate viscosity index improver containing a structural unit represented by the formula (1) in a proportion of 30 to 90 mol % and having a PSSI in an ultrasonic shear test of 15 or less; and a friction modifier, the engine oil composition has a kinematic viscosity at 100° C. of 4 to 8 mm 2 /s, and an HTHS viscosity at 150° C. of less than 2.6 mPa·s: [wherein R 1 represents hydrogen or a methyl group; and R 2 represents a linear or branched hydrocarbon group having a carbon number of 6 or less]:

1 . An engine oil composition comprising:
 a lubricating base oil having a kinematic viscosity at 100° C. of 1 to 5 mm 2 /s;   a poly(meth)acrylate viscosity index improver containing a structural unit represented by the following formula (1) in a proportion of 30 to 90 mol % and having a PSSI in an ultrasonic shear test of 15 or less; and   a friction modifier,   wherein the engine oil composition has a kinematic viscosity at 100° C. of 4 to 8 mm 2 /s, and an HTHS viscosity at 150° C. of less than 2.6 mPa·s:   
       
         
           
           
               
               
           
         
         wherein R I  represents hydrogen or a methyl group; and R 2  represents a linear or branched hydrocarbon group having a carbon number of 6 or less. 
       
     
     
         2 . The engine oil composition according to  claim 1 , wherein the viscosity index improver is a viscosity index improver having a PSSI in the ultrasonic shear test of 10 or less and a ratio of a molecular weight to the PSSI (Mw/PSSI) of 1×10 4  or more. 
     
     
         3 . The engine oil composition according to  claim 1 , wherein the friction modifier is an organic molybdenum friction modifier.