Low phosphorus lubricating oil composition

Abstract

This invention relates to a lubricating oil composition used in conjunction with a gasoline fuel having a sulphur content of less than 10 ppm by weight, characterised in that said oil composition has a phosphorus content of no more than 0.05% by weight. The feature of the invention is that the use of a low sulphur fuel enables the amount of anti-wear agents containing phosphorus such as eg ZDDP to be halved without any adverse effect on the anti-wear performance of the lubricating oil.

1 . Use in an internal combustion engine operating on gasoline fuel having a sulphur content of less than 10 ppm by weight, of a lubricating oil composition having a phosphorous content of no more than 0.05% by weight.  
     
     
         2 . The use according to  claim 1  wherein the gasoline fuel has less than 5 ppm by weight of sulphur.  
     
     
         3 . The use according to  claim 1  or  2  wherein the lubricating oil composition comprises Group II, Group III or Group IV basestock as defined by the API.  
     
     
         4 . The use according to any one of the preceding claims wherein the lubricating oil composition has a kinematic viscosity at 40° C. (KV 40 ) of about 75 cSt or less and at 100° C. (KV 100 ) of below 20 cSt; a pour point below −20° C.; a flash point of above 200° C.; a NOACK volatility of up to 15%; a TBN value of about 7 based on mg of KOH per gram (ASTM 2896-98); and a nitrogen content as measured by the Kjeldahl method of below 0.1% by mass.  
     
     
         5 . The use according to any one of the preceding claims wherein the lubricating oil composition is a 5W40 grade oil.  
     
     
         6 . The use according to any one of the preceding claims wherein the lubricating oil composition comprises in addition one or more additives selected from the group consisting of antioxidants, viscosity index improvers, anti-wear agents, demulsifiers, alkaline earth metal sulphonates and polyisobutenyl succinimides which are optionally borated.  
     
     
         7 . The use according to any one of the preceding claims wherein the lubricating oil composition comprises zinc dialkyldithiophosphate (ZDDP) as an anti-wear agent in an amount such that the phosphorus content of the composition is below 0.05% by weight.  
     
     
         8 . The use according to  claim 7  wherein the ZDDP has primary alkyl groups having 1-18 carbon atoms, secondary alkyl groups having 3-18 carbon atoms or a mixture of such primary and secondary alkyl groups.  
     
     
         9 . The use according to any one of the preceding claims  6 - 8  wherein the antioxidant is phenolic, aminic or mixtures thereof.  
     
     
         10 . A method of operating internal combustion engines which method comprises using a lubricating oil composition in conjunction with a gasoline fuel having a sulphur content of less than 10 ppm by weight, characterised in that said lubricating oil composition has a phosphorus content of no more than 0.05% by weight.  
     
     
         11 . A method for reducing wear in an internal combustion engine said method comprising using a lubricating oil composition in conjunction with a gasoline fuel having a sulphur content of less than 10 ppm by weight, characterised in that said lubricating oil composition has a phosphorus content of no more than 0.05% by weight.  
     
     
         12 . A method of reducing environmental pollution caused by the operation of an internal combustion engine whilst also reducing wear in said engine, said method comprising using a lubricating oil composition in conjunction with a gasoline fuel having a sulphur content of less than 10 ppm by weight, characterised in that said lubricating oil composition has a phosphorus content of no more than 0.05% by weight.