Lubricant compositions

Abstract

Lubricant compositions comprises a lubricant base oil blended with a boron-containing ashless dispersant (A) in an amount of 0.035 or more percent of boron by mass, and an alkaline earth metal sulfonate having a total base number of 50 to 500 mgKOH/g (B) in an amount of 0.01 or more percent of alkaline earth metal by mass, all the percentages being based on the total mass of the composition and if necessary a phosphorus additive. The lubricant compositions are superior in effect to enhance the dynamic- and static-friction coefficients in a wet clutch.

What is claimed is:  
     
         1 . A lubricant composition which comprises a lubricant base oil blended with a boron-containing ashless dispersant (A) in an amount of 0.035 or more percent of boron by mass, and an alkaline earth metal sulfonate having a total base number of 50 to 500 mgKOH/g (B) in an amount of 0.01 or more percent of alkaline earth metal by mass, all the percentages being based on the total mass of the composition.  
     
     
         2 . The lubricant composition according to    claim 1    wherein said ashless dispersant is a compound obtained by modifying a nitrogen-containing compound having in its molecule at least one alkyl or alkenyl group, or a derivative thereof, with a boric compound.  
     
     
         3 . The lubricant composition according to    claim 2    wherein said boric compound is selected from the group consisting of boric acid, boric acid salts, and borates.  
     
     
         4 . The lubricant composition according to    claim 1    which further contains a phosphorus additive (C).  
     
     
         5 . The lubricant composition according to    claim 4    wherein said phosphorus additive is blended in an amount of 0.005 to 0.2 percent by mass of phosphorus, based on the total mass of the composition.  
     
     
         6 . The lubricant composition according to any one of    claims 1    to    5    which further contains one or more additives selected from the group consisting of metallic detergents, friction modifiers, viscosity index improvers, extreme pressure agents, oxidation inhibitors, corrosion inhibitors, anti-foaming agents, and dyes.