Lubricating oil composition

Abstract

A lubricating oil composition which comprises (A) a base oil, (B) calcium salicylate having a base number of 50 to 300 mgKOH/g in an amount of 0.005 to 0.07 percent by mass in terms of calcium, (C) an SP type extreme pressure additive in an amount of 0.005 to 0.07 percent by mass in terms of phosphorous, (D) a specific succinimide compound in an amount of 0.1 to 6 percent by mass, and (E) a boron-containing ashless dispersant in an amount of 0.001 to 0.05 percent by mass in terms of boron, based on the total mass of the composition. The lubricating oil composition can prevent pitching of a transmission, resulting in the extended fatigue life thereof, and exhibits excellent and long-lasting anti-shudder properties.

1 . A lubricating oil composition which comprises (A) a base oil, (B) calcium salicylate having a base number of 50 to 300 mgKOH/g in an amount of 0.005 to 0.07 percent by mass in terms of calcium, (C) an SP type extreme pressure additive in an amount of 0.005 to 0.07 percent by mass in terms of phosphorous, (D) one or more compounds selected from the group consisting of succinimide compounds represented by formulas (3) and (4) below in an amount of 0.1 to 6 percent by mass, and (E) a boron-containing ashless dispersant in an amount of 0.001 to 0. 05 percent by mass in terms of boron, based on the total mass of the composition:  
       
         
           
           
               
               
           
         
       
       wherein R 11  is a straight-chain or branched hydrocarbon group having 8 to 30 carbon atoms, R 12  is hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, R 13  is a hydrocarbon group having 1 to 4 carbon atoms, and m is an integer of from 1 to 7;  
       
         
           
           
               
               
           
         
       
       wherein R 14  and R 15  are each independently a straight-chain or branched hydrocarbon group having 8 to 30 carbon atoms, and R 16  and R 17  are each independently a hydrocarbon group having 1 to 4 carbon atoms, and n is an integer of from 1 to 7.  
     
     
         2 . The lubricating oil composition according to  claim 1  wherein (C) SP type extreme pressure additive is at least one compound selected from the group consisting of phosphorus compounds represented by formulas (1) and (2) and salts thereof:  
       
         
           
           
               
               
           
         
       
       wherein at least one of X 1 , X 2 , and X 3  is sulfur and the remainder is oxygen, and R 1 , R 2 , and R 3  are each independently hydrogen or a hydrocarbon group having 1 to 30 carbon atoms; and  
       
         
           
           
               
               
           
         
       
       wherein X 4 , X 5 , and X 6  are each independently oxygen or sulfur, and R 4 , R 5 , and R 6  are each independently hydrogen or a hydrocarbon having 1 to 30 carbon atoms.  
     
     
         3 . The lubricating oil composition according to  claim 1  wherein (A) lubricating base oil comprises (A-1) a mineral and/or synthetic oil having a kinematic viscosity at 100° C. of 2 to 6 mm 2 /s in an amount of 60 to 99.5 percent by mass and (A-2) a heavy mineral oil having a kinematic viscosity at 100° C. of 10 to 50 mm 2 /s in an amount of 0.5 to 40 percent by mass, based on the total mass of the base oil.  
     
     
         4 . The lubricating oil composition according to  claim 1  which is used for automatic transmission or continuously variable transmissions.  
     
     
         5 . The lubricating oil composition according to  claim 1  which is used for transmissions equipped with wet clutches and wet brakes.