Lubricating Oil Composition

Abstract

The present disclosure provides a lubricating oil composition which has a viscosity much lower than that of a conventional lubricating oil composition, and which is excellent in metal fatigue life, wear resistance and electrical insulating properties. The lubricating oil composition according to the present disclosure comprises: (A) a lubricating base oil; and (B) from 0.6 to 4.0% by weight, based on the total weight of the lubricating oil composition, of a polydiene having a number average molecular weight of from 500 to 3,000 and containing a functional group on at least one end thereof. The above described lubricating oil composition does not comprise a viscosity index improver, and has a kinematic viscosity at 100° C. of not less than 1 and less than 5 mm 2 /s.

1 . A lubricating oil composition, comprising:
 (A) a lubricating base oil; and   (B) from 0.6 to 4.0% by weight, based on the total weight of the lubricating oil composition, of a polydiene having a number average molecular weight of from 500 to 3,000 and containing a functional group on at least one end thereof,   wherein the lubricating oil composition does not comprise a viscosity index improver, and wherein the lubricating oil composition has a kinematic viscosity at 100° C. of not less than 1 and less than 5 mm 2 /s.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the functional group in component (B) is selected from a carboxyl group, ester group, anhydrous carboxyl group, hydroxyl group, glycidyl group, urethane group and amino group. 
     
     
         3 . The lubricating oil composition according to  claim 2 , wherein the functional group is a hydroxyl group. 
     
     
         4 . The lubricating oil composition according to  claim 1 , further comprising (C) at least one selected from a phosphorus-based anti-wear agent and a phosphorus-based extreme pressure agent. 
     
     
         5 . The lubricating oil composition according to  claim 4 , wherein the phosphorus-based anti-wear agent is a zinc dialkyldithiophosphate. 
     
     
         6 . The lubricating oil composition according to  claim 5 , wherein the phosphorus-based extreme pressure agent is at least one selected from the group consisting of a phosphoric acid ester, a phosphorous acid ester, a thiophosphoric acid ester, a thiophosphorous acid ester, an acidic phosphoric acid ester, an acidic phosphorous acid ester, a acidic thiophosphoric acid ester and a acidic thiophosphorous acid ester, and an amine salt thereof. 
     
     
         7 . The lubricating oil composition according to  claim 1 , further comprising (D) a sulfur-based extreme pressure agent. 
     
     
         8 . The lubricating oil composition according to  claim 1 , further comprising (E) an ashless dispersant. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the lubricating base oil (A) has a kinematic viscosity at 100° C. of from 1 to 4 mm 2 /s. 
     
     
         10 . The lubricating oil composition according to  claim 1 , which is a gear oil for use in an automobile. 
     
     
         11 . The lubricating oil composition according to  claim 1 , which is a transmission oil for use in an automobile. 
     
     
         12 . The lubricating oil composition according to  claim 11 , which is a transmission oil for use in a hybrid vehicle.