Lubricating oil composition for spark-ignition internal combustion engine

Abstract

The lubricating oil composition for spark-ignition internal combustion engine according to the present invention is a lubricating oil composition to be used for a spark-ignition internal combustion engine including a piston having a piston ring, in which a total tension per piston of tensions applied to the piston ring is 30 N or less, the lubricating oil composition being a lubricating oil composition comprising a base oil, (A) an organic metal-based additive containing an alkali metal and/or an alkaline earth metal, and (B) an organic zinc-based additive, wherein a concentration of the component (A) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a metal content; a concentration of the component (B) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a zinc content; the product of the concentration (% by mass) of the component (A) and a base number (mgKOH/g) of the lubricating oil composition is 1.3 or less; the product of the concentration (% by mass) of the component (B) and an acid number (mgKOH/g) of the lubricating oil composition is 1.2 or less; and the lubricating oil composition has a Noack evaporation loss of 10% by mass or more and a kinematic viscosity at 100° C. of 9.3 mm 2 /s or less. The lubricating oil composition for spark-ignition internal combustion engine according to the present invention is capable of preventing a deterioration of the combustion state of a spark-ignition internal combustion engine.

1 . A lubricating oil composition for spark-ignition internal combustion engine that is a lubricating oil composition to be used for a spark-ignition internal combustion engine comprising a piston having a piston ring, in which a total tension per piston of tensions applied to the piston ring is 30 N or less, the lubricating oil composition being a lubricating oil composition comprising:
 a base oil,   (A) an organic metal-based additive containing an alkali metal and/or an alkaline earth metal, and   (B) an organic zinc-based additive,   wherein   a concentration of the component (A) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a metal content;   a concentration of the component (B) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a zinc content;   the product of the concentration (% by mass) of the component (A) and a base number (mgKOH/g) of the lubricating oil composition is 1.3 or less;   the product of the concentration (% by mass) of the component (B) and an acid number (mgKOH/g) of the lubricating oil composition is 1.2 or less; and   the lubricating oil composition has a Noack evaporation loss of 10% by mass or more and a kinematic viscosity at 100° C. of 9.3 mm 2 /s or less.   
     
     
         2 . The lubricating oil composition for spark-ignition internal combustion engine according to  claim 1 , further comprising an ashless base number improver having a base number of 1 mgKOH/g or more and 200 mgKOH/g or less on a basis of the total amount of the lubricating oil composition in an amount of 0.01% by mass or more as converted into a nitrogen content. 
     
     
         3 . The lubricating oil composition for spark-ignition internal combustion engine according to  claim 1 , wherein the component (A) is a metal-based detergent having a base number of 10 mgKOH/g or more and 600 mgKOH/g or less. 
     
     
         4 . The lubricating oil composition for spark-ignition internal combustion engine according to  claim 1 , wherein the component (B) is a zinc dialkyldithiophosphate and/or a zinc dialkyldioxyphosphate. 
     
     
         5 . The lubricating oil composition for spark-ignition internal combustion engine according to  claim 1 , further comprising an organic molybdenum-based additive, a content of the organic molybdenum-based additive on a basis of the total amount of the lubricating oil composition being 0.01% by mass or more and 0.07% by mass or less as converted into a molybdenum content. 
     
     
         6 . The lubricating oil composition for spark-ignition internal combustion engine according to  claim 1  any of  claims 1  to  5 , wherein the spark-ignition internal combustion engine is a gasoline engine. 
     
     
         7 . A method for producing a lubricating oil composition for spark-ignition internal combustion engine that is a lubricating oil composition to be used for a spark-ignition internal combustion engine comprising a piston having a piston ring, in which a total tension per piston of tensions applied to the piston ring is 30 N or less, the method comprising:
 blending a base oil with
 (A) an organic metal-based additive containing an alkali metal and/or an alkaline earth metal and 
 (B) an organic zinc-based additive in such a manner that 
   a concentration of the component (A) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a metal content;   a concentration of the component (B) on a basis of the total amount of the lubricating oil composition is 0.15% by mass or less as converted into a zinc content;   the product of the concentration (% by mass) of the component (A) and a base number (mgKOH/g) of the lubricating oil composition is 1.3 or less;   the product of the concentration (% by mass) of the component (B) and an acid number (mgKOH/g) of the lubricating oil composition is 1.2 or less; and   the lubricating oil composition has a Noack evaporation loss of 10% by mass or more and a kinematic viscosity at 100° C. of 9.3 mm 2 /s or less.   
     
     
         8 . A composition comprising:
 a base oil,   (A) an organic metal-based additive containing an alkali metal and/or an alkaline earth metal, and   (B) an organic zinc-based additive,   wherein   a concentration of the component (A) on a basis of the total amount of the composition is 0.15% by mass or less as converted into a metal content;   a concentration of the component (B) on a basis of the total amount of composition is 0.15% by mass or less as converted into a zinc content;   the product of the concentration (% by mass) of the component (A) and a base number (mgKOH/g) of the composition is 1.3 or less;   the product of the concentration (% by mass) of the component (B) and an acid number (mgKOH/g) of the composition is 1.2 or less; and   the composition has a Noack evaporation loss of 10% by mass or more and a kinematic viscosity at 100° C. of 9.3 mm 2 /s or less.