Lubricant composition

Abstract

A lubricating oil composition which comprises a base oil of lubricating oil having a kinematic viscosity of 3.5 to 10 mm 2 /s at 100° C. and a viscosity index of 100 or greater and (a) an ethylene-α-olefin copolymer having a number-average molecular weight of 2,500 to 25,000 and/or (b) a polymethacrylate having a number-average molecular weight of 10,000 to 30,000, wherein the kinematic viscosity of the composition is 5.6 to 15.0 mm 2 /s at 100° C. The lubricating oil exhibits excellent property for decreasing fuel consumption and can suppress generation of noise and vibration.

1 . A lubricating oil composition which comprises a base oil of lubricating oil having a kinematic viscosity of 3.5 to 10 mm 2 /s at 100° C. and a viscosity index of 100 or greater and (a) an ethylene-α-olefin copolymer having a number-average molecular weight of 2,500 to 25,000 and/or (b) a polymethacrylate having a number-average molecular weight of 10,000 to 30,000, wherein a kinematic viscosity of the composition is 5.6 to 15.0 mm 2 /s at 100° C. 
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the kinematic viscosity of the lubricating oil composition is 5.6 to 12.5 mm 2 /s at 100° C. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the kinematic viscosity of the base oil of lubricating oil is 3.5 to 6 mm 2 /s at 100° C. 
     
     
         4 . The lubricating oil composition according to  claim 1 , which further comprises at least one additive selected from the group consisting of an antioxidant, an extreme pressure agent, an antiwear agent, an oiliness improver, a detergent-dispersant, a viscosity index improver and a pour point depressant. 
     
     
         5 . (canceled) 
     
     
         6 . An internal combustion engine comprising the lubricating oil composition according to  claim 1 .