Marine Engine Lubrication

Abstract

A two-stroke or four-stroke marine engine lubricating oil composition comprising an oil of lubricating viscosity in a major amount and (A) additives, in respective minor amounts; and (B) a viscosity modifier in the form of a polymer comprising a core and a plurality of polymeric arms extending therefrom. Preferably, brightstock is completely or substantially absent from the composition.

What is claimed is: 
     
         1 . A two-stroke or four-stroke marine engine lubricating oil composition comprising an oil of lubricating viscosity in a major amount and
 (A) additives, in respective minor amounts; and   (B) a viscosity modifier in the form of a polymer comprising a core and a plurality of polymeric arms extending therefrom, in an amount in the range of 0.05 to 6 mass %;   wherein the composition includes less than 0.5 mass % of brightstock; and   wherein the two-stroke marine engine lubricating oil composition has a TBN of 40 to 100 mg KOH/g as measured using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as measured using ASTM D2896.   
     
     
         2 . The composition as claimed in  claim 1 , wherein the arms of the polymer comprise a hydrogenated isoprene-butadiene copolymer, a hydrogenated styrene-isoprene-butadiene copolymer, a hydrogenated isoprene-styrene copolymer or a hydrogenated butadiene-styrene copolymer. 
     
     
         3 . The composition as claimed in  claim 1 , wherein the polymeric arms comprise a linear diblock copolymer. 
     
     
         4 . The composition as claimed in  claim 1 , wherein the polymer has a number average molecular weight of 10,000-700,000. 
     
     
         5 . The composition as claimed in  claim 1 , in the form of a marine diesel cylinder lubricant. 
     
     
         6 . The composition as claimed in  claim 1 , in the form of a trunk piston engine oil. 
     
     
         7 . A method of lubricating a cross-head marine diesel engine comprising supplying a composition as claimed in  claim 1  to the piston/cylinder assembly of the engine. 
     
     
         8 . A method of lubricating a trunk piston marine diesel engine comprising supplying a composition as claimed in  claim 1  to the engine. 
     
     
         9 . A method of reducing the amount of brightstock in a two-stroke or four-stroke marine engine lubricating oil composition comprising an oil of lubricating viscosity in a major amount and (A) additives, in respective minor amounts; the method comprising the step of replacing, in part or in full, the brightstock with (B) a viscosity modifier in the form of a polymer comprising a core and a plurality of polymeric arms extending therefrom, in an amount in the range of 0.05 to 6 mass %. 
     
     
         10 . The method as claimed in  claim 9 , wherein (B) substantially replaces the brightstock so that the composition includes less than 0.5 mass % of brightstock. 
     
     
         11 . The method as claimed in  claim 9 , wherein the composition includes less than 0.1 mass % of brightstock. 
     
     
         12 . The method as claimed in  claim 9 , wherein the two-stroke marine engine lubricating oil composition has a TBN of 40 to 100 mg KOH/g, as measured using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as measured using ASTM D2896.