Lubricant compositions for direct injection engines

Abstract

The invention is directed to a method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine by supplying to the sump a lubricant composition which contains an oil of lubricating viscosity and an ashless dispersant. The ashless dispersant may be selected from succinimide compounds prepared from aliphatic or aromatic amines.

1 . A method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine comprising supplying to the engine a lubricant composition comprising a base oil of lubricating viscosity and an ashless dispersant. 
     
     
         2 . The method of  claim 1 , wherein the engine is operated under a load with a brake mean effective pressure (BMEP) of greater than or equal to 10 bars. 
     
     
         3 . The method of  claim 2 , wherein the engine is operated at speeds less than or equal to 3,000 rpm. 
     
     
         4 . The method of  claim 1 , wherein the engine is fueled with a liquid hydrocarbon fuel, a liquid non-hydrocarbon fuel, or mixtures thereof. 
     
     
         5 . The method of  claim 1 , wherein the engine is fueled by natural gas, liquefied petroleum gas (LPG), compressed natural gas (CNG), or mixtures thereof. 
     
     
         6 . The method of  claim 1 , wherein the ashless dispersant is a polyalkenyl dispersant derived from acylated polyisobutylene. 
     
     
         7 . The method of  claim 1 , wherein the ashless dispersant comprises a polyisobutylene succinimide compound. 
     
     
         8 . The method of  claim 7 , wherein the polyisobutylene succinimide compound is prepared from an amine comprising one or more of aliphatic polyamines, aromatic amines, polyether amines, and mixtures thereof. 
     
     
         9 . The method of  claim 6 , wherein the acylated polyisobutylene is prepared by a chlorine process, a thermal process, a free radical polymerization process, or combinations thereof. 
     
     
         10 . The method of  claim 1 , wherein the lubricant composition further comprises at least one other additive selected from an ashless antioxidant, a metal containing overbased detergent, a phosphorus-containing anti-wear additive, a friction modifier, and a polymeric viscosity modifier. 
     
     
         11 . The method of  claim 10 , wherein the ashless antioxidant is derived from a 2,6-dialkyl phenol. 
     
     
         12 . The method of  claim 10 , wherein the ashless antioxidant is a diarylamine compound. 
     
     
         13 . The method of  claim 1 , wherein the ashless dispersant is present in an amount from 1.0 to 6.5 weight percent of the lubricant composition. 
     
     
         14 . The method of  claim 1 , wherein the lubricating composition comprises at least 50 weight % of Group II base oil, Group III base oil, or mixtures thereof. 
     
     
         15 . The method of  claim 1 , wherein the low speed pre-ignition events are reduced to less than 20 LSPI events per 100,000 combustion events. 
     
     
         16 . The method of  claim 1 , wherein there is a reduction in the number of LSPI events of at least 10 percent. 
     
     
         17 . A method for reducing low speed pre-ignition events in a spark-ignited direct injection internal combustion engine operated under a load with a brake mean effective pressure (BMEP) of greater than or equal to 10 bars and at speeds less than or equal to 3,000 rpm, comprising supplying to the engine a lubricant composition comprising a base oil of lubricating viscosity and a post-treated ashless dispersant, wherein the post-treated ashless dispersant comprises the reaction product of an ashless dispersant and a boron compound.