Lubricating oil composition

Abstract

Disclosed is a lubricating oil composition comprising: a lubricating base oil having a kinematic viscosity at 100° C. of 3.5 to 4.5 mm 2 /s, a viscosity index of 145 or greater, and an urea adduct value of 2 to 7% by mass; and a poly(meth)acrylate pour-point depressant containing structural units represented by the formula (1): wherein R 1 represents a hydrogen atom and the like, R 2 represents an alkyl group; based on the total amount of the units contained in the depressant, a ratio of the units wherein the R 2 is a methyl group is 0 to 10 mol %, a ratio of the units wherein the R 2 is an alkyl group having 12C or greater is 90 to 100 mol %; the alkyl group having 12C or greater has an average number of 13-16C; the depressant has a weight-average molecular weight of 10,000 to 200,000.

1 . A lubricating oil composition comprising:
 a lubricating base oil having a kinematic viscosity at 100° C. of 3.5 to 4.5 mm 2 /s, a viscosity index of 145 or greater, and an urea adduct value of 2 to 7% by mass; and   a poly(meth)acrylate pour-point depressant containing structural units represented by the following formula (1):   
       
         
           
           
               
               
           
         
         wherein in the formula (1), R 1  represents a hydrogen atom or a methyl group, and R 2  represents an alkyl group; 
         based on the total amount of the structural units represented by the formula (1) contained in the poly(meth)acrylate pour-point depressant, a ratio of the structural units represented by the formula (1) wherein the R 2  is a methyl group is 0 to 10 mol %, and a ratio of the structural units represented by the formula (1) wherein the R 2  is an alkyl group having 12 or greater carbon atoms is 90 to 100 mol %; 
         the alkyl group having 12 or greater carbon atoms in the poly(meth)acrylate pour-point depressant has an average number of carbon atoms of 13 to 16; and 
         the poly(meth)acrylate pour-point depressant has a weight-average molecular weight of 10,000 to 200,000. 
       
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the ratio of structural units represented by the formula (1) wherein the R 2  is an alkyl group having 20 or greater carbon atoms is 0 to 10 mol %, based on the total amount of structural units represented by the formula (1) contained in the poly(meth)acrylate pour-point depressant. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein a content ratio of the poly(meth)acrylate pour-point depressant is 0.01 to 2.0% by mass based on the total amount of the lubricating oil composition. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein R 1  represents a methyl group. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the composition has a MRV viscosity at −40° C. of 10,000 to 60,000 mPa·s.