Lubricating oil composition

Abstract

A lubricating oil composition contains: a first base oil with a kinematic viscosity at 100 degrees C. in a range from 1.5 mm 2 /s to 3.5 mm 2 /s; a second base oil with a kinematic viscosity at 100 degrees C. in a range more than 3.5 mm 2 /s but not more than 100 mm 2 /s; polymethacrylate with a mass average molecular weight in a range from 1×10 4 to 4×10 4 ; and a sulfur compound. The lubricating oil composition has a kinematic viscosity at 100 degrees C. in a range from 5 mm 2 /s to 6 mm 2 /s and a viscosity index of 200 or more.

1 . A lubricating oil composition, the lubricating oil composition comprising:
 a first base oil with a kinematic viscosity at 100 degrees C. in a range of 1.5 mm 2 /S to 3.5 mm 2 /S;   a second base oil with a kinematic viscosity at 100 degrees C. in a range more than 3.5 mm 2 /s and less than 100 mm 2 /s;   polymethacrylate with a mass average molecular weight in a range of 1×10 4  to 4×10 4 ; and   a sulfur compound;   wherein the lubricating oil composition has a kinematic viscosity at 100 degrees C. in a range of 5 mm 2 /s to 6 mm 2 /s and a viscosity index of 200 or more.   
     
     
         2 . The lubricating oil composition of  claim 1 , wherein:
 a blending amount of the first base oil based on a total composition amount is expressed by A and a blending amount of the second base oil based on the total composition amount is expressed by B; and   the blending amount A and the blending amount B are expressed in formula [1],
   0.6 ≦A /( A+B )<1   [1]
 
   
     
     
         3 . The lubricating oil composition of  claim 2 , wherein the blending amount B of the second base oil is 10 mass % or more. 
     
     
         4 . The lubricating oil composition of  claim 1 , wherein a blending amount of the polymethacrylate is in a range of 1 mass % to 16 mass % based on the total composition amount. 
     
     
         5 . The lubricating oil composition of  claim 1 , wherein a blending amount of the sulfur compound is 0.03 mass % or more based on the total composition amount. 
     
     
         6 . The lubricating oil composition of  claim 1 , wherein the sulfur compound comprises sulfur in an amount of 20 mass % or more based on the sulfur compound. 
     
     
         7 . The lubricating oil composition of  claim 1 , further comprising at least one agent selected from the group consisting of detergent dispersant, an antiwear agent, a friction modifier, a rust inhibitor, a metal deactivator, an antifoaming agent and an antioxidant. 
     
     
         8 . A lubricating oil composition for an automatic transmission, comprising the lubricating oil composition of  claim 1 .