Lubricating Oil Compositions

Abstract

A lubricating oil composition, a method of reducing low-speed pre-ignition (LSPI) in a direct-injected spark-ignited internal combustion engine, and a use of a lubricant composition to reduce LSPI events in such an engine. Preferably, the composition comprises a detergent package comprising a borated calcium detergent, wherein the detergent package provides a calcium content in the composition of at least 0.12 mass %, based on the total mass of the composition, and wherein the borated calcium detergent provides a boron content in the composition of at least 100 ppmm, based on the total mass of the composition. Optionally, the composition comprises a first detergent comprising a calcium detergent, and a second detergent comprising a borated calcium detergent.

What is claimed is: 
     
         1 . A lubricating oil composition comprising a first detergent comprising a calcium detergent and a second detergent comprising a borated calcium detergent;
 wherein, the first and second detergents together provide a calcium content, as measured by ASTM 4951, in the lubricating oil composition of at least 0.12 mass %, based on the total mass of the lubricating oil composition, and wherein the second detergent provides a boron content, as measured by ASTM D5185, in the lubricating oil composition of at least 100 ppmm, based on the total mass of the lubricating oil composition.   
     
     
         2 . A lubricating oil composition according to  claim 1 , wherein the first detergent has a calcium content of from 2 mass % to 16 mass %, based on the mass of the first detergent, andtor the second detergent has a calcium content of from 4 mass % to 16 mass % , based on the mass of the second detergent. 
     
     
         3 . A lubricating oil composition according to  claim 1 , wherein the second detergent has a boron content of from 1 mass % to 10 mass %, based on the mass of the second detergent. 
     
     
         4 . A lubricating oil composition according to  claim 1 , wherein the first and second detergents together provide a calcium content in the lubricating oil composition of at least 0.14 mass, based on the total mass of the lubricating oil composition. 
     
     
         5 . A lubricating oil composition according to  claim 1 , wherein the second detergent provides a boron content in the lubricating oil composition of at least 150 ppmm, based on the total mass of the lubricating oil composition. 
     
     
         6 . A lubricating oil composition according to  claim 1 , wherein:
 the first detergent comprises a calcium phenate, a calcium sulfonate and/or a calcium salicylate; and   the second detergent comprises a borated calcium phenate, a borated calcium sulfonate and/or a borated calcium salicylate.   
     
     
         7 . A lubricating oil composition according to  claim 1 , wherein the second detergent comprises a borated analogue of the calcium detergent of the first detergent. 
     
     
         8 . A lubricating oil composition according to  claim 1 , wherein the second detergent comprises calcium and boron in a calcium mass % to boron mass % ratio of 1:Z, based on the mass of the second detergent, wherein Z is at least 0.1. 
     
     
         9 . A lubricating oil composition according to  claim 8 , wherein Z is from 0.1 to 4. 
     
     
         10 . A lubricating oil composition according to  claim 1 , wherein the first detergent and the second detergent are present in a ratio of first detergent mass % to second detergent mass % of 1:X, based on the total mass of the lubricating oil composition, wherein X is at least 0.1. 
     
     
         11 . A lubricating oil composition according to  claim 10 , wherein X is from 0.1 to 10. 
     
     
         12 . A lubricating oil composition according to  claim 1 , wherein at least 50%, of the boron content of the lubricating oil composition is provided by the second detergent. 
     
     
         13 . A lubricating oil composition according to  claim 12 , wherein 100%, of the boron content of the lubricating oil composition is provided by the second detergent.