Lubricating oil composition

Abstract

A lubricating oil composition for a gas engine containing: a base oil (A), at least one overbased calcium detergent (B) selected from the group consisting of calcium salicylate (B1) and calcium phenate (B2), alkenyl succinimide (C), and a hindered amine-based antioxidant (D), where the content (X) of calcium atoms derived from the component (B) is less than 0.090% by mass based on the total amount of the lubricating oil composition; the content (Y) of calcium carbonate contained in the component (B) is 0.060% by mass or more based on the total amount of the lubricating oil composition; the content of boron atoms derived from the component (C) is less than 0.020% by mass based on the total amount of the lubricating oil composition, and the content of the component (D) is more than 0.20% by mass based on the total amount of the lubricating oil composition.

1 : A lubricating oil composition, comprising:
 a base oil (A),   at least one overbased calcium detergent (B) selected from the group consisting of calcium salicylate (B1) and calcium phenate (B2),   an alkenyl succinimide (C), and   a hindered amine-based antioxidant (D),   wherein   a content (X) of calcium atoms derived from the at least one overbased calcium detergent (B) is less than 0.090% by mass based on a total amount of the lubricating oil composition;   a content (Y) of calcium carbonate contained in the at least one overbased calcium detergent (B) is 0.060% by mass or more based on the total amount of the lubricating oil composition;   a content of boron atoms derived from the alkenyl succinimide (C) is less than 0.020% by mass based on the total amount of the lubricating oil composition; and   a content of the hindered amine-based antioxidant (D) is more than 0.20% by mass based on the total amount of the lubricating oil composition.   
     
     
         2 : The lubricating oil composition according to  claim 1 , wherein a ratio [(X)/(Y)] of the content (X) of calcium atoms derived from the at least one overbased calcium detergent (B) to the content (Y) of calcium carbonate contained in the at least one overbased calcium detergent (B) is 0.20 to 0.90. 
     
     
         3 : The lubricating oil composition according to  claim 1 , wherein the content (X) of calcium atoms derived from the at least one overbased calcium detergent (B) is less than 0.080% by mass based on the total amount of the lubricating oil composition. 
     
     
         4 : The lubricating oil composition according to  claim 1 , wherein the at least one overbased calcium detergent (B) comprises at least calcium salicylate (B1). 
     
     
         5 : The lubricating oil composition according to  claim 1 , comprising substantially no metal sulfonate. 
     
     
         6 : The lubricating oil composition according to  claim 1 , wherein the alkenyl succinimide (C) comprises both a non-boron-modified alkenyl succinimide (C1) and a boron-modified alkenyl succinimide (C2). 
     
     
         7 : The lubricating oil composition according to  claim 1 , wherein a content ratio [N/Ca] of nitrogen atoms derived from the alkenyl succinimide (C) to calcium atoms derived from the at least one overbased calcium detergent (B) is 1.20 or less. 
     
     
         8 : The lubricating oil composition according to  claim 1 , further comprising a zinc dithiophosphate (E). 
     
     
         9 : The lubricating oil composition according to  claim 1 , wherein a sulfated ash content of the lubrication oil composition is less than 0.50% by mass based on the total amount of the lubricating oil composition. 
     
     
         10 : A gas engine to which the lubricating oil composition according to  claim 1  is applied. 
     
     
         11 : A method for lubricating a gas engine, comprising:
 applying the lubricating oil composition according to  claim 1  to the gas engine.