Lubricating oil composition

Abstract

A lubricating oil composition including: a lubricant base oil having a kinematic viscosity at 40° C. of 6.0 to 12.0 mm 2 /s; (A) a succinimide dispersant having a polyisobutenyl group having a number average molecular weight of no less than 800, in an amount of no less than 80 mass ppm in terms of nitrogen and no more than 2.7 mass % as the entire compound; (B) a condensation reaction product of an alkyl- or alkenyl-succinic acid having a C8-30 alkyl or alkenyl group or anhydride thereof and a polyamine, or a modified product thereof, or any combination thereof, in an amount of 50 to 1300 mass ppm in terms of nitrogen, wherein the product of the weight average molecular weight of the component (A) and the amount of the component (A) as the entire compound (mass %) is no more than 16,000.

1 . A lubricating oil composition comprising:
 (O) a lubricant base oil comprising at least one mineral base oil or at least one synthetic base oil or any combination thereof, and having a kinematic viscosity at 40° C. of 6.0 to 12.0 mm 2 /s;   (A) a condensation reaction product of a polyisobutenylsuccinic acid or anhydride thereof and a first polyamine, or a modified product thereof, or any combination thereof, in an amount of no less than 80 mass ppm in terms of nitrogen and no more than 2.7 mass % as an entire compound on the basis of the total mass of the composition, the polyisobutenylsuccinic acid having a polyisobutenyl group, the polyisobutenyl group having a number average molecular weight of no less than 800;   (B) a condensation reaction product of an alkyl- or alkenyl-succinic acid having a C8-30 alkyl or alkenyl group or anhydride thereof and a second polyamine, or a modified product thereof, or any combination thereof, in an amount of 50 to 1300 mass ppm in terms of nitrogen on the basis of the total mass of the composition,   wherein a product of a weight average molecular weight (unit: Da) of the component (A) and the amount of the component (A) as the entire compound (unit: mass %) is no more than 16,000.   
     
     
         2 . The lubricating oil composition according to  claim 1 , further comprising:
 (C) at least one calcium sulfonate detergent overbased with calcium carbonate, or at least one calcium salicylate detergent overbased with calcium carbonate, or any combination thereof, in an amount of no less than 10 mass ppm and less than 100 mass ppm in terms of calcium on the basis of the total mass of the composition.   
     
     
         3 . The lubricating oil composition according to  claim 1 , further comprising:
 (D) at least one amine antioxidant and at least one phenol antioxidant, in an amount of 0.1 to 3.0 mass % as a total amount thereof, on the basis of the total mass of the composition.   
     
     
         4 . The lubricating oil composition according to  claim 1 , further comprising:
 optionally (E) at least one phosphorus-containing compound, or at least one sulfur-containing compound comprising at least one sulfur atom having a formal oxidation number of no more than +II in a molecule thereof, or any combination thereof, in an amount of no more than 1000 mass ppm in terms of a total amount of phosphorus content and sulfur content on the basis of the total mass of the composition.   
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein a relation of the following equation (1) is met, 
       
         
           
             
               
                 
                   
                     B 
                     ≥ 
                     
                       max 
                       ⁢ 
                          
                       
                         ( 
                         
                           50 
                           , 
                           
                             f 
                             ⁡ 
                             ( 
                             A 
                             ) 
                           
                         
                         ) 
                       
                     
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         
           
             
               
                 f 
                 ⁡ 
                 ( 
                 A 
                 ) 
               
               = 
               
                 100 
                 × 
                 
                   ( 
                   
                     
                       - 
                       10.5 
                     
                     + 
                     
                       14.1 
                       × 
                       
                         
                           ( 
                           
                             
                               A 
                               100 
                             
                             - 
                             0.5 
                           
                           ) 
                         
                         
                           - 
                           0.3 
                         
                       
                     
                   
                   ) 
                 
               
             
           
         
         wherein in the equation (1), A represents the amount (unit: mass ppm) of the component (A) in terms of nitrogen on the basis of the total mass of the composition; and B represents the amount (unit: mass ppm) of the component (B) in terms of nitrogen on the basis of the total mass of the composition. 
       
     
     
         6 . The lubricating oil composition according to  claim 1 , further comprising:
 optionally (F) at least one polyalkyl (meth)acrylate having a weight average molecular weight of more than 25,000, in an amount of no more than 5.0 mass % on the basis of the total mass of the composition.   
     
     
         7 . The lubricating oil composition according to  claim 1 , further comprising:
 optionally, at least one polymer having a weight average molecular weight of no more than 25,000, in an amount of less than 0.1 mass % on the basis of the total mass of the composition.   
     
     
         8 . The lubricating oil composition according to  claim 1 , which is used to lubricate an automatic transmission. 
     
     
         9 . The lubricating oil composition according to  claim 1 , which is used to lubricate an electric motor. 
     
     
         10 . A method for lubricating an automatic transmission and an electric motor,
 the automatic transmission and the electric motor being comprised in an automobile,   the method comprising:   supplying the lubricating oil composition as defined in  claim 1  to the automatic transmission of the automobile; and   supplying the lubricating oil composition to the electric motor of the automobile.