Fuel economy lubricating oil composition for lubricating diesel engines

Abstract

A lubricating oil composition for internal combustion engines comprising a base oil having and lubricating viscosity and additives composed of a) a salt of an alkali metal or alkaline earth metal and an alkylsalicylate and/or an alkylcarboxylate, b) a nitrogen atom-containing ashless dispersant and/or a nitrogen atom-containing dispersive viscosity index improver, c) a neutral salt of a fatty acid and a fatty amine, and d) oxidation inhibitor, is effective for lubricating diesel engines using a low sulfur-content fuel, even though it has a low sulfated ash content, a low sulfur content and a low phosphorus content.

1 . A lubricating oil composition for lubricating internal combustion engines which has a sulfated ash content of 1.1 wt. % or less, a sulfur content of 0.5 wt. % or less, and a phosphorus content of 0.12 wt. % or less and which comprises a base oil having a lubricating viscosity and the following additive components:
 a) a metal-containing detergent comprising at least one of an alkali metal or alkaline earth metal alkylsalicylate and an alkali metal or alkaline earth metal alkylcarboxylate in an amount of 0.01 to 0.4 wt. % in terms of an amount of metal contained in the composition;   b) at least one of a nitrogen-containing ashless dispersant and a nitrogen-containing dispersive viscosity index improver in an amount of 0.01 to 0.3 wt. % in terms of a nitrogen amount;   c) a neutral salt of a fatty acid with a fatty amine in ah amount of 0.1 to 5 wt. %; and   d) an oxidation inhibitor in an amount of 0.1 to 5 wt. %.   
     
     
         2 . The lubricating oil composition of  claim 1 , in which the neutralized salt of a fatty acid with a fatty amine is a neutral salt of a fatty acid having 8 to 30 carbon atoms and a fatty amine having 8 to 30 carbon atoms. 
     
     
         3 . The lubricating oil composition of  claim 2 , in which the fatty acid is an unsaturated fatty acid and the fatty amine is a saturated fatty amine. 
     
     
         4 . The lubricating oil composition of  claim 3 , in which the fatty acid is an unsaturated linear chain fatty acid. 
     
     
         5 . The lubricating oil composition of  claim 4 , in which the unsaturated linear chain fatty acid is oleic acid. 
     
     
         6 . The lubricating oil composition of  claim 3 , in which the fatty amine is a saturated linear chain fatty amine. 
     
     
         7 . The lubricating oil composition of  claim 6 , in which the saturated linear chain fatty amine is stearyl amine. 
     
     
         8 . The lubricating oil composition of  claim 1 , in which the neutral salt of a fatty acid with a fatty amine is contained in an amount of 0.1 to 2 wt. %. 
     
     
         9 . The lubricating oil composition of  claim 1 , in which the metal-containing detergent comprising at least one of an alkali metal or alkaline earth metal alkylsalicylate and an alkali metal or alkaline earth metal alkylcarboxylate is contained in an amount of 0.1 to 0.4 wt. % in terms of an amount of metal contained in the composition. 
     
     
         10 . The lubricating oil composition of  claim 1 , in which the base oil having a lubricating viscosity has a saturated component of 85 wt. % or more, a viscosity index of 110 or more, and a sulfur content of 0.01 wt. % or less. 
     
     
         11 . The lubricating oil composition of  claim 1 , in which the nitrogen-containing ashless dispersant has a weight average molecular weight in the range of 4,500 to 20,000. 
     
     
         12 . The lubricating oil composition of  claim 1 , which further comprises a zinc dihydrocarbyldithiophosphate or a zinc dihydrocarbylphosphate in an amount of 0.01 to 0.12 wt. % in terms of an amount of a phosphorus amount. 
     
     
         13 . The lubricating oil composition of  claim 1 , which has a TBN in the range of 2 to 15 mg·KOH/g and is used for lubricating diesel engines. 
     
     
         14 . A process for lubricating a diesel engine comprising operating the engine using the lubricating oil composition of  claim 1 .