Lubricating oil composition

Abstract

Use of a lubricating oil composition comprising, or made by admixing, a major amount of oil of lubricating viscosity, and minor amounts of (A) a dispersant additive composition and (B) a detergent additive composition, wherein the oil composition gives a sulfated ash content of at most 1.0 mass %; has a total base number (TBN) of 4 to 9.5; has at least 0.08 mass % of nitrogen derived from the dispersant additive composition, based on the mass of the oil composition; and has at least 25 mmol of soap per 1000 g of the oil composition derived from the detergent additive composition, to improve the cleanliness of pistons in an engine.

1 . A lubricating oil composition comprising, or made by admixing, a major amount of oil of lubricating viscosity, and minor amounts of (A) a dispersant additive composition and (B) a detergent additive composition, wherein the oil composition gives a sulfated ash content of at most 1.0 mass %; has a total base number (TBN) of from about 4 to 9.5; has at least 0.08 mass % of nitrogen derived from the dispersant additive composition, based on the mass of the oil composition; and has at least 25 mmol of soap per 1000 g of the oil composition derived from the detergent additive composition.  
     
     
         2 . An oil composition according to  claim 1 , wherein the oil of lubricating viscosity comprises a Group III basestock.  
     
     
         3 . An oil composition, according to  claim 1 , wherein the dispersant additive composition comprises a borated dispersant and non-borated dispersant.  
     
     
         4 . An oil composition, according to  claim 1 , wherein at most 35% of the mmol of soap in the lubricating oil composition is derived from a detergent having a TBN greater than 150.  
     
     
         5 . An oil composition according to  claim 1 , wherein the detergent additive composition comprises at least one metal detergent based on one or more organic acid not containing sulfur.  
     
     
         6 . An oil composition according to  claim 5 , wherein said at least one metal detergent based on one or more organic acid not containing sulphur is a salicylate detergent.  
     
     
         7 . An oil composition according to  claim 6 , wherein said salicylate detergent is a calcium salicylate detergent having a TBN of, at most, 150.  
     
     
         8 . An oil composition according to  claim 5 , wherein the detergent additive composition consists of a calcium salicylate having a TBN of 150 to 200 and a calcium salicylate having a TBN of at most 80.  
     
     
         9 . An oil composition according to  claim 1 , further comprising one or more of an antioxidant composition comprising an aromatic amine, a hindered phenol and, a molybdenum compound.  
     
     
         10 . An oil composition according to  claim 1 , further comprising a zinc dialkyldithiophosphate containing secondary alkyl groups in a major molar proportion, based on the total amount of alkyl groups.  
     
     
         11 . An oil composition according to  claim 1 , wherein the oil composition has a sulfur content of at most 0.25 mass %, based on the mass of the oil composition.  
     
     
         12 . An oil composition according to  claim 1 , wherein the oil composition has a phosphorus content of at most 0.09 mass %, based on the mass of the oil composition.  
     
     
         13 . An oil composition according to  claim 9 , wherein the oil composition has a molybdenum content of at most 300, based on the mass of the oil composition.  
     
     
         14 . An oil composition according to  claim 1 , wherein the oil composition has a boron content of at most 150 ppm, based on the mass of the oil composition.  
     
     
         15 . An oil composition, according to  claim 1 , in which at least one dispersant comprises a polyisobutenyl succinimide prepared using high vinylidene polyisobutene.  
     
     
         16 . A method of lubricating a compression-ignited internal combustion engine comprising operating the engine and lubricating the engine with a lubricating oil composition as claimed in  claim 1 .  
     
     
         17 . A method of improving piston cleanliness and reducing the ring-sticking tendencies of a compression-ignited internal combustion engine comprising adding to the engine a lubricating oil composition as claimed in  claim 1 .  
     
     
         18 . A combination comprising the crankcase of a compression-ignited internal combustion engine, and a lubricating oil composition as claimed in  claim 1 .  
     
     
         19 . A method of improving piston cleanliness in an internal combustion engine comprising lubricating said internal combustion engine with a lubricating oil composition comprising (1) a dispersant additive composition in an amount that provides at least 0.085 mass % of nitrogen and (2) a detergent additive composition in an amount that provides at least 25 mmol of soap per 1000 g of the oil composition, which lubricating oil composition gives a sulfated ash of most 1.0 mass % and has a TBN of 4 to 9.5.  
     
     
         20 . An additive concentrate for preparing a lubricating oil composition comprising an oleaginous carrier fluid, a dispersant additive composition and a detergent additive composition, in such a proportion as to provide a lubricating oil composition as defined in  claim 1  when the oil composition contains 10 to 30 mass %, based on the mass of the oil composition, of additives, said additives excluding viscosity modifier and pour point depressant additives.