Lubricant composition

Abstract

A marine diesel cylinder lubricant composition for a marine diesel engine running on fuel having a sulphur content of less than 1.5%, the composition having a total base number, as determined according to ASTM D2896, of more than 30 and less than 70, and comprising at least 40 wt % of an oil of lubricating viscosity, and at least one detergent prepared from at least two surfactants, one of which is a salicylate. The marine diesel cylinder lubricant composition demonstrates good ability to reduce deposit formation, especially on pistons. The marine diesel cylinder lubricant composition also demonstrates good lubrication at temperatures above 250° C.

1 . A method of operating a marine diesel engine on fuel having at most 1.5% sulphur, the method comprising: 
 lubricating the marine diesel engine with a cylinder lubricant having a total base number of more than 30 and less than 70, the cylinder lubricant including    (a) at least 40 wt % of an oil of lubricating viscosity, and    (b) at least one detergent prepared from at least two surfactants, one of which is a salicylate.    
     
     
         2 . The method of  claim 1  in which the detergent has a total base number in the range of 250 to 500.  
     
     
         3 . The method of  claim 1  in which the marine diesel engine includes a cylinder liner operating at a temperature greater than 250° C.  
     
     
         4 . The method of  claim 3  in which the cylinder liner operates at a temperature greater than 300° C.  
     
     
         5 . The method of  claim 1  in which the detergent includes at least 5 mass % of salicylate.  
     
     
         6 . The method of  claim 1  in which the detergent includes at least 5 mass % of phenate and at least 5 mass % of sulphonate.  
     
     
         7 . The method of  claim 1  which has a base number of less than 60 and more than 35.  
     
     
         8 . The method of  claim 1  in which the cylinder lubricant includes at least one of the following: a dispersant, an anti-wear agent, an anti-oxidant, a pour point depressant, an anti-foamant and a demulsifier.  
     
     
         9 . The method of  claim 1  in which the cylinder lubricant has a temperature of scuffing initiation of at least about 338° C.  
     
     
         10 . The method of  claim 1  in which one of the surfactants is not a salicylate.