Lubricant oil composition

Abstract

Provided is a lubricating oil composition, which is used in an internal combustion engine employing a fuel containing at least one kind selected from a hydrogenated product of natural fats and oils, a transesterification product of natural fats and oils, and a hydrogenated product of a transesterification product of natural fats and oils, which includes an alkali metal borate or a hydrate thereof in an alkali metal-corresponding amount of 10 to 1,000 ppm by mass in terms of total amount of the lubricating oil composition, and which can satisfactorily exhibit cleanness even in the case where the above-mentioned fuel is mixed therein or the case where ash content thereof is low.

1 . A lubricating oil composition, comprising an alkali metal borate or a hydrate thereof in an amount of 10 to 1,000 ppm by mass in terms of an alkali metal, based on a total amount of the lubricating oil composition. 
     
     
         2 . A lubricating oil composition according to  claim 1 , further comprising, in addition to (A) the alkali metal borate or the hydrate thereof, at least one selected from the group consisting of (B) to (E):
 (B) at least one compound selected from the group consisting of:
 a substituted hydroxyaromatic carboxylate ester derivative represented by general formula (I): 
   
       
         
           
           
               
               
           
         
         where: R 1  and R 2 , which are identical to or different from each other, each represent an organic group having 6 or more carbon atoms; a, b, c, d, and e each represent an integer satisfying relations of 1≦a≦3, 1≦b≦3, 0≦c≦3, 1≦d≦3, 1≦d≦3, 1≦e≦3, 3≦(a+b+e)≦6, and 1≦(c+d)≦5; and when a plurality of R 1 's and a plurality of R 2 's are present, each of the plurality of R 1 's and the plurality of R 2 's are identical to or different from one another within the respective groups; and
 a substituted hydroxyaromatic carboxylate ester derivative represented by general formula (II): 
 
       
       
         
           
           
               
               
           
         
         where: R 3 , R 4 , and R 5 , which are identical to or different from one another, each represent an organic group having 6 or more carbon atoms; f, g, h, i, j, k, and m each represent an integer satisfying relations of 0≦f≦3, 0≦g≦3, 1≦(f+g)≦3, 0≦h≦4, 0≦i≦3, 1≦(h+i)≦6, 0≦j≦3, 1≦k≦3, 1≦m≦3, 0≦(f+h)≦4, 1≦(g+i+m)≦4, and 1≦(j+k)≦5; and when a plurality of R 3 's, a plurality of R 4 's, and a plurality of R 5 's are present, each of the plurality of R 3 's, the plurality of R 4 's, and the plurality of R 5 's are identical to or different from one another within the respective groups; 
         (C) a phenol-based antioxidant; 
         (D) an amine-based antioxidant; and 
         (E) a molybdenum-based antioxidant. 
       
     
     
         3 . A lubricating oil composition according to  claim 1 , comprising a sulfated ash content of 1.2 mass % or less. 
     
     
         4 . An internal combustion engine, comprising the lubricating oil composition according to  claim 1  and a fuel comprising at least one of a hydrogenated product of natural fats and oils, a transesterification product of natural fats and oils, and a hydrogenated product of a transesterification product of natural fats and oils.