Lubricant compositions for direct injection engines

Abstract

A lubricant additive, an crankcase lubricant composition and a method for reducing intake valve deposits in a spark ignition direct injection (SIDI) engine. The lubricant additive includes (a) as a viscosity index improver, one or more ethylene/olefin copolymers derived from at least 40 mole % ethylene monomer units in an amount ranging from about 0.15 to about 0.95 wt. % based on a total weight of the lubricant composition, and (b) from about 0.1 to about 5.0 percent by weight based on a total weight of a lubricant composition of an aromatic compound having a boiling point under standard atmospheric conditions of from about 190° to about 270° C., wherein the lubricant additive is effective to reduce intake valve deposits in a SIDI engine.

What is claimed is: 
     
         1 . A lubricant additive effective for reducing intake valve deposits in a spark ignition direct injection (SIDI) engine comprising (a) as a viscosity index improver, one or more ethylene/olefin copolymers derived from at least 40 mole % ethylene monomer units in an amount ranging from about 0.15 to about 0.95 wt. % based on a total weight of the lubricant composition, and (b) from about 0.1 to about 5.0 percent by weight based on a total weight of a lubricant composition of an aromatic compound having a boiling point under standard atmospheric conditions of from about 190° to about 270° C., wherein the lubricant additive is effective to reduce intake valve deposits in a SIDI engine. 
     
     
         2 . The lubricant additive of  claim 1 , wherein the aromatic compound is selected from the group consisting of 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-6-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, o-cresol, m-cresol, p-cresol, and mixtures of two or more of the foregoing. 
     
     
         3 . The lubricant additive of  claim 1 , wherein the aromatic compound comprises 2,6-di-tert-butylphenol. 
     
     
         4 . A lubricant composition comprising the lubricant additive of  claim 1 , wherein the lubricant additive comprises from about 0.5 to about 2.0 percent by weight based on a total weight of the lubricant composition of component (b). 
     
     
         5 . A lubricant booster additive for addition to a crankcase of a SIDI engine comprising the lubricant additive of  claim 1 . 
     
     
         6 . A method for reducing intake valve deposits in a spark ignition direct injection (SIDI) engine comprising providing to a crankcase of the engine a lubricant composition comprising the lubricant additive of  claim 1 . 
     
     
         7 . The method of  claim 1 , wherein the aromatic compound is selected from the group consisting of 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-6-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, o-cresol, m-cresol, p-cresol, and mixtures of two or more of the foregoing. 
     
     
         8 . The method of  claim 7 , wherein the aromatic compound comprises 2,6-di-tert-butylphenol. 
     
     
         9 . The method of  claim 6 , wherein the amount of component (a) in the lubricant composition ranges from about 0.4 to about 0.85 percent by weight based on a total weight of a lubricant composition. 
     
     
         10 . The method of  claim 6 , wherein the amount of aromatic compound in the lubricant composition ranges from about 0.5 to about 2.0 percent by weight based on a total weight of a lubricant composition. 
     
     
         11 . A crankcase lubricant composition for a spark ignition direct injection (SIDI) engine comprising a lubricant additive comprising (a) as a viscosity index improver, one or more ethylene/olefin copolymers derived from at least 40 mole % ethylene monomer units in an amount ranging from about 0.15 to about 0.95 wt. % based on a total weight of the lubricant composition, and (b) from about 0.1 to about 5.0 percent by weight based on a total weight of a lubricant composition of an aromatic compound having a boiling point under standard atmospheric conditions of from about 190° to about 270° C., wherein the lubricant additive is effective to reduce intake valve deposits in a SIDI engine. 
     
     
         12 . The crankcase lubricant composition of  claim 11 , wherein the aromatic compound is selected from the group consisting of 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-6-methylphenol, 2-tert-butylphenol, 4-tert-butylphenol, o-cresol, m-cresol, p-cresol, and mixtures of two or more of the foregoing. 
     
     
         13 . The crankcase lubricant composition of  claim 11 , wherein the amount of aromatic compound in the lubricant composition ranges from about 0.1 to about 5.0 percent by weight based on a total weight of a lubricant composition. 
     
     
         14 . The crankcase lubricant composition of  claim 11 , wherein the amount of component (a) in the lubricant composition ranges from about 0.4 to about 0.85 percent by weight based on a total weight of a lubricant composition. 
     
     
         15 . The crankcase lubricant composition of  claim 11 , further comprising one or more of the members of the group selected from detergents, dispersants, friction modifiers, antioxidants, rust inhibitors, emulsifiers, demulsifiers, corrosion inhibitors, antiwear agents, metal dihydrocarbyl dithiophosphates, ash-free amine phosphate salts, antifoam agents, and pour point depressants. 
     
     
         16 . The crankcase lubricant composition of  claim 11 , further comprising an oil-soluble titanium-containing additive.