Method for preventing or reducing low speed pre-ignition in direct injected spark-ignited engines with molybdenum-containing lubricant compositions

Abstract

A lubricant composition for a direct injected, boosted, spark ignited internal combustion engine that comprises one or more molybdenum-containing compounds and one or more calcium detergents is disclosed. This disclosure also relates to a method for reducing or preventing low speed pre-ignition (LSPI) in the course of at least one oil change interval.

What is claimed is: 
     
         1 . A method for reducing or preventing low speed pre-ignition (LSPI) in a direct-injected, boosted, spark-ignited, internal combustion engine, said method comprising the step of lubricating the engine with a used or aged lubricant composition comprising:
 (i) one or more oils of lubricating viscosity;   (ii) one or more molybdenum-containing compounds, in an amount providing the lubricant composition with at least about 100 ppm of molybdenum, based upon the total weight of the composition; and   (iii) one or more calcium detergents, in an amount providing the lubricant composition with at least about 1000 ppm of calcium, based upon the total weight of the composition;   wherein the used or aged lubricant composition lubricates the engine in the course of at least one oil change interval.   
     
     
         2 . The method of  claim 1 , wherein the (ii) one or more molybdenum-containing compounds, are in an amount providing the lubricant composition with at least about 850 ppm of molybdenum, based upon the total weight of the composition; and the (iii) one or more calcium detergents are in an amount providing the lubricant composition with at least about 1800 ppm of calcium, based upon the total weight of the composition. 
     
     
         3 . The method of  claim 1 , wherein the (ii) one or more molybdenum-containing compounds are in an amount providing the lubricant composition with about 100 ppm to about 850 ppm of molybdenum, based upon the total weight of the composition; and the (iii) one or more calcium detergents are in an amount providing the lubricant composition with about 1000 to about 1450 ppm of calcium, based upon the total weight of the composition. 
     
     
         4 . The method of  claim 1 , wherein the and the (iii) one or more calcium detergents are in an amount providing the lubricant composition with less than about 2400 ppm, based upon the total weight of the composition. 
     
     
         5 . The method of  claim 1 , wherein the one or more molybdenum-containing compounds are selected from the group consisting of: molybdenum-amine complexes, molybdenum dithiophosphates, and molybdenum dithiocarbamates. 
     
     
         6 . The method of  claim 1 , wherein the one or more molybdenum-containing compounds are selected from the group consisting of: molybdenum-amine complexes and molybdenum dithiophosphates. 
     
     
         7 . The method of  claim 6 , wherein the molybdenum-amine complex is a molybdenum succinimide complex. 
     
     
         8 . The method of  claim 1 , wherein the direct-injected, boosted, spark-ignited, internal combustion engine is a downsized engine or an engine that ranges in size from 0.5 liters to 3.6 liters. 
     
     
         9 . The method of  claim 1 , wherein the direct-injected, boosted, spark-ignited, internal combustion engine is operated at speeds between 500 and 3000 rpm. 
     
     
         10 . The method of  claim 1 , wherein the direct-injected, boosted, spark-ignited, internal combustion engine is operated under a load with a brake mean effective pressure (BMEP) of from about 12 to about 30 bars. 
     
     
         11 . The method of  claim 1 , wherein the LSPI events occurring while the engine is operated are less than 10 per 100,000 combustion events. 
     
     
         12 . The method of  claim 1 , wherein the method provides a reduction in the number of LSPI events of at least 50%. 
     
     
         13 . The method of  claim 1 , wherein the one or more calcium detergents are selected from the group consisting of a carboxylate detergent. 
     
     
         14 . The method of  claim 1 , wherein the one or more calcium detergents are selected from the group consisting of a salicylate, phenate, or sulfonate detergent. 
     
     
         15 . The method of  claim 1 , wherein the lubricant composition further comprises at least one other additive selected from an ashless dispersant, an antioxidant, an anti-wear additive, a friction modifier, and a polymeric viscosity modifier. 
     
     
         16 . The method of  claim 1 , wherein the at least one oil change interval is at least 3000 miles. 
     
     
         17 . The method of  claim 1 , wherein the at least one oil change interval is at least 5000 miles.