Lubricating Oil Composition

Abstract

The present disclosure provides a lubricating oil composition which is excellent in metal fatigue life, wear resistance and electrical insulating properties, even when the composition has a reduced viscosity. The lubricating oil composition according to the present disclosure comprises: (A) a lubricating base oil; (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; and (C) at least one selected from a phosphorus-based anti-wear agent and a phosphorus-based extreme pressure agent, the at least one agent being contained in such an amount that the content of phosphorus is from 50 to 500 ppm by weight based on the total weight of the lubricating oil composition.

1 . A lubricating oil composition, comprising:
 (A) a lubricating base oil;   (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; and   (C) at least one selected from a phosphorus-based anti-wear agent and a phosphorus-based extreme pressure agent, the at least one agent being contained in such an amount that the content of phosphorus is from 50 to 500 ppm by weight based on the total weight of the lubricating oil composition.   
     
     
         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 , wherein the phosphorus-based anti-wear agent is a zinc dialkyldithiophosphate. 
     
     
         5 . The lubricating oil composition according to  claim 1 , 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. 
     
     
         6 . The lubricating oil composition according to  claim 1 , further comprising (D) a sulfur-based extreme pressure agent. 
     
     
         7 . The lubricating oil composition according to  claim 1 , further comprising (E) an ashless dispersant. 
     
     
         8 . The lubricating oil composition according to  claim 1 , wherein the lubricating oil composition has a kinematic viscosity at 100° C. of not less than 1 mm 2 /s and less than 5 mm 2 /s. 
     
     
         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.