Method for improving engine fuel efficiency

Abstract

A method for improving fuel efficiency, while maintaining or improving wear protection, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a HTHS viscosity of less than 2.6 cP at 150° C. In one form, the formulated oil has a composition that includes a lubricating oil base stock as a major component, and zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components. The lubricating oil has a HTHS viscosity of less than 2.6 cP at 150° C. The composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the formulated oil or lubricating engine oil.

What is claimed is: 
     
         1 . A method for improving fuel efficiency, while maintaining or improving wear protection, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil having a HTHS viscosity of less than 2.6 cP at 150° C., said formulated oil having a composition comprising a lubricating oil base stock as a major component, and a zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components; wherein said composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the formulated oil; and wherein said composition is sufficient for the formulated oil to pass wear protection requirements of one or more engine tests selected from TU3M, Sequence IIIG, Sequence IVA and OM646LA. 
     
     
         2 . The method of  claim 1  wherein the base oil comprises a Group I, Group II, Group III, Group IV or Group V base oil. 
     
     
         3 . The method of  claim 1  wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock. 
     
     
         4 . The method of  claim 1  wherein the alkali metal detergents and alkaline earth metal detergents are selected from metallic salicylates and sulfonates, and wherein the metallic salicylates and sulfonates are selected from calcium and magnesium. 
     
     
         5 . The method of  claim 1  wherein the ZDDP is a secondary dialkyl dithio phosphate. 
     
     
         6 . The method of  claim 1  wherein said composition contains less than 1 weight percent of the viscosity index improver, based on the total weight of the formulated oil. 
     
     
         7 . The method of  claim 1  wherein the oil base stock is present in an amount of from 70 weight percent to 95 weight percent, the zinc dialkyl dithio phosphate (ZDDP) is present in an amount of from 0.4 weight percent to 1.2 weight percent, and the mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents, is present in an amount of from 1.0 weight percent to 6.0 weight percent, based on the total weight of the formulated oil. 
     
     
         8 . The method of  claim 1  wherein said composition contains less than 0.5 weight percent of the viscosity index improver, based on the total weight of the formulated oil. 
     
     
         9 . The method of  claim 1  wherein the formulated oil has a HTHS viscosity of less than 2.4 cP at 150° C. 
     
     
         10 . The method of  claim 1  wherein the lubricating oil is a passenger vehicle engin oil (PVEO). 
     
     
         11 . A lubricating engine oil having a composition comprising a lubricating oil base stock as a major component, and a zinc dialkyl dithio phosphate, a mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents; and a viscosity index improver, as minor components; wherein said lubricating engine oil has a HTHS viscosity of less than 2.6 cP at 150° C.; wherein said composition contains less than 2 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil; and wherein said composition is sufficient for the lubricating engine oil to pass wear protection requirements of one or more engine tests selected from TU3M, Sequence IIIG, Sequence IVA and OM646LA. 
     
     
         12 . The lubricating engine oil of  claim 11  wherein the oil base stock comprises a Group I, Group II Group III, Group IV or Group V base oil. 
     
     
         13 . The lubricating engine oil of  claim 11  wherein the lubricating oil base stock comprises a poly alpha olefin (PAO) or gas-to-liquid (GTL) oil base stock. 
     
     
         14 . The lubricating engine oil of  claim 11  wherein the alkali metal detergents and alkaline earth metal detergents are selected from metallic salicylates and sulfonates, and wherein the metallic salicylates and sulfonates are selected from calcium and magnesium. 
     
     
         15 . The lubricating engine oil of  claim 11  wherein the ZDDP is a secondary dialkyl dithio phosphate. 
     
     
         16 . The lubricating engine oil of  claim 11  wherein said composition contains less than 1 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil. 
     
     
         17 . The lubricating engine oil of  claim 11  wherein the oil base stock is present in an amount of from 70 weight percent to 95 weight percent, the zinc dialkyl dithio phosphate (ZDDP) is present in an amount of from 0.4 weight percent to 1.2 weight percent, and the mixture of (i) at least two alkali metal detergents, (ii) at least two alkaline earth metal detergents, or (iii) one or more alkali metal detergents and one or more alkaline earth metal detergents, is present in an amount of from 1.0 weight percent to 6.0 weight percent, based on the total weight of the lubricating engine oil. 
     
     
         18 . The lubricating engine oil of  claim 11  wherein said composition contains less than 0.5 weight percent of the viscosity index improver, based on the total weight of the lubricating engine oil. 
     
     
         19 . The lubricating engine oil of  claim 11  which has a HTHS viscosity of less than 2.4 cP at 150° C. 
     
     
         20 . The lubricating engine oil of  claim 11  comprising a passenger vehicle engine oil (PVEO).