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 method of lubricating an internal combustion engine employing 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, said method comprising lubricating said engine with a lubricating oil composition comprising:
 (A) 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;   (C) a phenol-based antioxidant;   (D) an amine-based antioxidant; and   (E) a molybdenum-based antioxidant.   
     
     
         2 : A method according to  claim 1 , wherein said lubricating oil composition further comprises:
 (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≦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. 
       
     
     
         3 : A method according to  claim 2 , wherein said lubricating oil composition further comprises a substituted hydroxyaromatic carboxylate ester derivative represented by general formula (I). 
     
     
         4 : A method according to  claim 2 , wherein said lubricating oil composition further comprises a substituted hydroxyaromatic carboxylate ester derivative represented by general formula (II). 
     
     
         5 . The method according to  claim 1 , wherein said method is a method of lubricating an internal combustion engine employing a fuel comprising a hydrogenated product of natural fats and oils. 
     
     
         6 : The method according to  claim 1 , wherein said method is a method of lubricating an internal combustion engine employing a fuel comprising a transesterification product of natural fats and oils. 
     
     
         7 : The method according to  claim 1 , wherein said method is a method of lubricating an internal combustion engine employing a fuel comprising a hydrogenated product of a transesterification product of natural fats and oils.