Lubricating oil composition for internal combustion engine

Abstract

A lubricating oil composition for an internal combustion engine including: (A) a lubricant base oil having a kinematic viscosity at 100° C. of 2 to 5 mm 2 /s; (B) a metallic detergent in an amount of 500 to 2500 mass ppm in terms of Ca and 100 to 1000 mass ppm in terms of Mg, on the basis of the total mass of the composition, the metallic detergent including both (B1) a Ca-containing metallic detergent and (B2) a Mg-containing metallic detergent; (C) a boron-containing additive in an amount of 50 to 1000 mass ppm in terms of boron on the basis of the total mass of the composition, wherein the boron-containing additive is oil-soluble or oil-dispersible and is stable in oil, and wherein the boron-containing additive may compose at least a part of the component (B); and (D) an oil-soluble organic Mo compound in an amount of 100 to 2000 mass ppm in terms of Mo on the basis of the total mass of the composition, wherein a mass ratio (MB/Mg) of boron content of the composition (MB) to Mg content of the composition (Mg) is 0.5 to 10.

1 . A lubricating oil composition for an internal combustion engine, the composition comprising:
 (A) a lubricant base oil having kinematic viscosity at 100° C. of 2 to 5 mm 2 /s;   (B) a metallic detergent in an amount of 500 to 2500 mass ppm in terms of calcium and 100 to 1000 mass ppm in terms of magnesium, on the basis of the total mass of the composition, the metallic detergent comprising both (B1) a calcium-containing metallic detergent and (B2) a magnesium-containing metallic detergent;   (C) a boron-containing additive in an amount of 50 to 1000 mass ppm in terms of boron on the basis of the total mass of the composition, wherein the boron-containing additive is oil-soluble or oil-dispersible and is stable in oil, and wherein the boron-containing additive may compose at least a part of the component (B); and   (D) an oil-soluble organic molybdenum compound in an amount of 100 to 2000 mass ppm in terms of molybdenum on the basis of the total mass of the composition,   wherein a mass ratio (MB/Mg) of boron content of the composition (MB) to magnesium content of the composition (Mg) is 0.5 to 10; and   the composition satisfies one or more requirement selected from the following (i) to (iii):   (i) the boron content of the composition is no less than 270 mass ppm on the basis of the total mass of the composition;   (ii) the component (C) comprises a boric acid salt-overbased metallic detergent, wherein the boric acid salt-overbased metallic detergent may compose at least a part of the component (B1) or the component (B2) or the combination thereof; and   (iii) the mass ratio (MB/Mg) of the boron content of the composition (MB) to the magnesium content of the composition (Mg) is no less than 0.8.   
     
     
         2 . The lubricating oil composition according to  claim 1 , wherein the component (C) comprises a boric acid salt-overbased alkaline earth metal salicylate. 
     
     
         3 . The lubricating oil composition according to  claim 1 , wherein the component (B) comprises an overbased magnesium sulfonate. 
     
     
         4 . The lubricating oil composition according to  claim 1 , wherein the component (D) comprises a molybdenum dithiocarbamate in an amount of 100 to 2000 mass ppm in terms of molybdenum on the basis of the total mass of the composition. 
     
     
         5 . The lubricating oil composition according to  claim 1 , wherein the composition has HTHS viscosity at 150° C. of 1.9 to 2.7 mPa·s. 
     
     
         6 . The lubricating oil composition according to  claim 1 , wherein the composition has HTHS viscosity at 150° C. of 1.9 to 2.4 mPa·s. 
     
     
         7 . The lubricating oil composition according to  claim 1 , wherein the composition has a NOACK evaporation loss at 250° C. of no more than 15 mass %.