Lubricating oil composition

Abstract

Provided is a lubricating oil composition which has an excellent effect of reducing the friction coefficient even when a member having a low surface roughness in a low oil temperature region is lubricated, by means of a lubricating oil composition which contains a mineral base oil (A), a polymer (B) having a weight average molecular weight (Mw) of 100 to 15,000, and a molybdenum-based friction modifier (M) and has a kinematic viscosity at 40° C. of 35.0 mm2/s or less.

1 . A lubricating oil composition comprising a mineral base oil (A), a polymer (B) having a weight average molecular weight (Mw) of 100 to 15,000, and a molybdenum-based friction modifier (M), wherein the lubricating oil composition has a kinematic viscosity at 40° C. of 35.0 mm2/s or less. 
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the content of the polymer (B) is 0.1 to 5.0% by mass based on the total amount of the lubricating oil in terms of solid content. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the polymer (B) is a polyolefin (B-1). 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the weight average molecular weight (Mw) of the polymer (B) is 1,000 to 11,000. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the molybdenum-based friction modifier (M) comprises two or more selected from a binuclear molybdenum dithiocarbamate, a trinuclear molybdenum dithiocarbamate, and a molybdenum amine complex. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the content of the molybdenum-based friction modifier (M) is 50 to 2,000 ppm by mass in terms of molybdenum atom based on the total amount of the composition. 
     
     
         7 . The lubricating oil composition according to  claim 1 , which is used in an engine provided with a member having a maximum height roughness (Rz) of the surface of less than 0.45 μm. 
     
     
         8 . A method for lubricating an automobile engine, comprising lubricating the automobile engine with the lubricating oil composition of  claim 1  wherein the automobile engine is equipped with a hybrid mechanism or an idling stop mechanism. 
     
     
         9 . A method for lubricating an engine, comprising lubricating an engine provided with a member having a maximum height roughness (Rz) of the surface of less than 0.45 μm using the lubricating oil composition according to  claim 1 .