Lubricating oil composition

Abstract

A lubricating oil composition which achieves extended anti-shudder durability without causing a decrease in the metal-to-metal friction coefficient, even when the viscosity of the composition is reduced. The lubricating oil composition includes (A) a lubricant base oil, (C) (C-1) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of 4,000 to 7,000, (C-2) a succinimide compound or boronated succinimide compound having a weight-average molecular weight of more than 7,000 to 10,000, and (D) a phosphorus-based extreme pressure agent, the lubricating oil composition does not include zinc dithiophosphate and may optionally include a sulfur-based extreme pressure agent, provided that the content of sulfur-based extreme pressure agent is no more than 0.1 percent by weight of the lubricating oil composition.

1 . A lubricating oil composition comprising
 (A) a lubricant base oil,   (C) (C-1) a succinimide compound or a boronated succinimide compound having a weight-average molecular weight of 4,000 to 7,000, and (C-2) a succinimide compound or a boronated succinimide compound having a weight-average molecular weight of more than 7,000 and not more than 10,000, and   (D) a phosphorus-based extreme pressure agent,
 wherein the lubricating oil composition does not comprise zinc dithiophosphate, and the lubricating oil composition may optionally comprise a sulfur-based extreme pressure agent, provided that a content of the sulfur-based extreme pressure agent is not more than 0.1 percent by weight based on the lubricating oil composition. 
   
     
     
         2 . The lubricating oil composition according to  claim 1 , comprising, as a part or all of the component (A), 5 to 30 percent by weight, based on a total weight of the lubricating oil composition, of a poly-α-olefin or α-olefin copolymer having a kinematic viscosity at 100° C. of 6 to 80 mm 2 /s, and further comprising (B) a polymethacrylate having a weight-average molecular weight of 15,000 to 40,000. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein a part or all of component (C-1) and component (C-2) is a boronated succinimide compound. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein a content of boron is 0.1 to 3 percent by weight based on the weight of the boronated succinimide compound in each of component (C-1) and component (C-2). 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein a weight ratio of component (C-1) to component (C-2), i.e., (C-2)/(C-1), is 1 to 10. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the succinimide compound is represented by following formula (1) or (2): 
       
         
           
           
               
               
           
         
         wherein R 1  is each independently an alkyl or alkenyl group having 40 to 400 carbon atoms, m is an integer of 1 to 20, and n is an integer of 0 to 20. 
       
     
     
         7 . The lubricating oil composition according to  claim 1 , having a kinematic viscosity at 100° C. of 3 to 10 mm 2 /s. 
     
     
         8 . The lubricating oil composition according to  claim 1 , having a viscosity index of 150 or higher. 
     
     
         9 . The lubricating oil composition according to  claim 1 , wherein the phosphorus-based extreme pressure agent (D) is at least one selected from an acidic phosphate, acidic phosphite, phosphate, phosphite, and amine salts thereof, phosphoric acid, and phosphorus acid. 
     
     
         10 . The lubricating oil composition according to  claim 9 , wherein the phosphorus-based extreme pressure agent (D) is at least one selected from an acidic phosphate, acidic phosphite, phosphate, phosphite and amine salts thereof, combined with at least one selected from phosphoric acid and phosphorus acid. 
     
     
         11 . The lubricating oil composition according to  claim 1 , further comprising (E) a metallic detergent. 
     
     
         12 . The lubricating oil composition according to  claim 1 , further comprising (F) an ether sulfolane compound. 
     
     
         13 . The lubricating oil composition according to  claim 1 , which is for a non-stage transmission. 
     
     
         14 . The lubricating oil composition according to  claim 2 , wherein a part or all of component (C-1) and component (C-2) is a boronated succinimide compound. 
     
     
         15 . The lubricating oil composition according to  claim 2 , wherein a content of boron is 0.1 to 3 percent by weight based on the weight of the boronated succinimide compound in each of component (C-1) and component (C-2). 
     
     
         16 . The lubricating oil composition according to  claim 2 , wherein a weight ratio of component (C-1) to component (C-2), i.e., (C-2)/(C-1), is 1 to 10. 
     
     
         17 . The lubricating oil composition according to  claim 2 , wherein the succinimide compound is represented by following formula (1) or (2): 
       
         
           
           
               
               
           
         
         wherein R 1  is each independently an alkyl or alkenyl group having 40 to 400 carbon atoms, m is an integer of 1 to 20, and n is an integer of 0 to 20. 
       
     
     
         18 . The lubricating oil composition according to  claim 2 , having a kinematic viscosity at 100° C. of 3 to 10 mm 2 /s. 
     
     
         19 . The lubricating oil composition according to  claim 2 , having a viscosity index of 150 or higher. 
     
     
         20 . The lubricating oil composition according to  claim 2 , wherein the phosphorus-based extreme pressure agent (D) is at least one selected from an acidic phosphate, acidic phosphite, phosphate, phosphite, and amine salts thereof, phosphoric acid, and phosphorus acid.