Lubricating oil composition

Abstract

Lubricating oil compositions particularly suitable for automatic transmissions comprising a lubricating base oil, (A) a boron-containing ashless dispersant in an amount of 0.004 to 0.05 percent by mass in terms of boron, based on the total mass of the composition, (B) an alkaline earth metal-based detergent with a base number of 0 to 500 mgKOH/g in an amount of 0.01 percent by mass or more in terms of an alkaline earth metal, based on the total mass of the composition, and (C) a sulfur-based additive in an amount of 0.01 to 0.3 percent by mass in terms of sulfur, based on the total mass of the composition and having excellent anti-wear properties and improved fatigue life by inhibiting pitching.

1 . A lubricating oil composition which comprises a lubricating base oil, (A) a boron-containing ashless dispersant in an amount of 0.004 to 0.05 percent by mass in terms of boron, based on the total mass of the composition, (B) an alkaline earth metal-based detergent with a base number of 0 to 500 mgKOH/g in an amount of 0.01 percent by mass or more in terms of an alkaline earth metal, based on the total mass of the composition, and (C) a sulfur-based additive in an amount of 0.01 to 0.3 percent by mass in terms of sulfur, based on the total mass of the composition.  
     
     
         2 . The lubricating oil composition according to  claim 1  wherein Component (A) is a succinimide modified with a boron compound.  
     
     
         3 . The lubricating oil composition according to  claim 1  wherein Component (B) is an alkaline earth metal calcium or an alkaline earth metal magnesium.  
     
     
         4 . The lubricating oil composition according to  claim 1  wherein Component (B) is sulfonate or salicylate.  
     
     
         5 . The lubricating oil composition according to  claim 1  wherein Component (C) is at least one compound selected from the group consisting of (C-1) thiazole compounds, (C-2) thiadiazole compounds, (C-3) dithiocarbamate compounds, (C-4) molybdenum dithiocarbamate compounds, (C-5) dihydrocarbylpolysulfide compounds, and (C-6) sulfurized ester compounds.  
     
     
         6 . The lubricating oil composition according to  claim 1  wherein it is used in transmissions for automobiles.