Lubricating oil composition

Abstract

Provided is a lubricating oil composition for use in internal-combustion engines, containing a base oil (A), an ashless dispersant (B) containing a non-boronated alkenylsuccinic acid imide (B1) and a boronated alkenylsuccinic acid imide (B2), a thiadiazole compound (C), and an aromatic carboxylate (D) having one or more hydroxy groups, wherein the content of the component (C) is 0.2 to 1.2% by mass based on the total amount of the lubricating oil composition, the content of a zinc dithiophosphate is, as calculated in terms of zinc atoms, less than 500 ppm by mass based on the total amount of the lubricating oil composition, and the content of a metal-based detergent is, as calculated in terms of metal atoms, less than 600 ppm by mass based on the total amount of the lubricating oil composition.

1 . A lubricating oil composition for use in internal-combustion engines, comprising:
 a base oil (A),   an ashless dispersant (B) containing a non-boronated alkenylsuccinic acid imide (B1) and a boronated alkenylsuccinic acid imide (B2),   a thiadiazole compound (C), and   an aromatic carboxylate (D) having one or more hydroxy groups, wherein:   the content of the component (C) is 0.2 to 1.2% by mass based on the total amount of the lubricating oil composition,   the content of a zinc dithiophosphate is, as calculated in terms of zinc atoms, less than 500 ppm by mass based on the total amount of the lubricating oil composition, and   the content of a metal-based detergent is, as calculated in terms of metal atoms, less than 600 ppm by mass based on the total amount of the lubricating oil composition.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the content ratio of the component (D) to the component (B2) [(D)/(B2)] is, as a ratio by mass, 0.1 to 5.0. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the content of the component (D) is, based on the total amount of the lubricating oil composition, 0.5 to 15.0% by mass. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the component (D) is one or more selected from a compound (D1) represented by the following general formula (d-1) and a compound (D2) represented by the following general formula (d-2): 
       
         
           
           
               
               
           
         
         wherein R 1  to R 5  each independently represent a hydrocarbon group having 1 to 50 carbon atoms; 
         a represents an integer of 1 to 3, b represents an integer of 1 to 3, c represents an integer of 0 to 3, d represents an integer of 1 to 3, e represents an integer of 1 to 3, a+b+e is an integer of 3 to 6, and c+d is an integer of 1 to 5; 
         f represents an integer of 0 to 3, g represents an integer of 0 to 3, and f+g is an integer of 1 to 3; 
         h represents an integer of 0 to 4, i represents an integer of 0 to 3, and h+i is an integer of 1 to 6; 
         j represents an integer of 0 to 3, k represents an integer of 1 to 3, and j+k is an integer of 1 to 5; 
         m represents an integer of 1 to 3, and f+g+h+i+m is an integer of 3 to 8. 
       
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the content of the component (B2) is, as calculated in terms of boron atoms and based on the total amount of the lubricating oil composition, 200 to 3000 ppm by mass. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the content ratio of the boron atom to the nitrogen atom in the component (B2) [B/N] is, as a ratio by mass, 0.3 to 2.5. 
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein the content of the component (B1) is, as calculated in terms of nitrogen atoms and based on the total amount of the lubricating oil composition, 400 to 3000 ppm by mass. 
     
     
         8 . The lubricating oil composition according  claim 1 , wherein the content ratio of the boron atom to the nitrogen atom in the component (B) [B/N] is, as a ratio by mass, 0.10 to 1.30. 
     
     
         9 . The lubricating oil composition according to  claim 1  wherein the component (C) is a compound represented by the following general formula (c-1): 
       
         
           
           
               
               
           
         
         wherein p and q each independently represent an integer of 0 to 5, p+q is 1 or more, and r and s each independently represent an integer of 1 to 5; 
         R a  and R b  each independently represent a hydrogen atom, a hydrocarbon group, or a hetero atom-containing group that contains one or more of an oxygen atom, a nitrogen atom and a sulfur atom. 
       
     
     
         10 . The lubricating oil composition according to  claim 1 , wherein the content of the molybdenum compound is, as calculated in terms of molybdenum and based on the total amount of the lubricating oil composition, less than 100 ppm by mass. 
     
     
         11 . The lubricating oil composition according to  claim 1 , wherein the phosphorus atom content is, based on the total amount of the lubricating oil composition, less than 400 ppm by mass. 
     
     
         12 . The lubricating oil composition according to  claim 1 , wherein the sulfated ash content is, based on the total amount of the lubricating oil composition, less than 0.30% by mass.