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) an olefin copolymer viscosity modifier. 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 an olefin copolymer 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 determined using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as determined using ASTM D2896.   
     
     
         2 . The composition as claimed in  claim 1 , wherein the olefin copolymer is a copolymer of two or more monomers of C 2 -C 30  olefins. 
     
     
         3 . The composition as claimed in  claim 2 , wherein the olefin copolymer is a copolymer of ethylene with a C 3 -C 30  olefin. 
     
     
         4 . The composition as claimed in  claim 3 , wherein the olefin copolymer is a copolymer of ethylene with propylene. 
     
     
         5 . The composition as claimed in  claim 1 , wherein the copolymer is an ethylene copolymer containing 15 to 90 mass % of ethylene and 10 to 85 mass % of one or more C 3 -C 28  alpha-olefins. 
     
     
         6 . The composition as claimed in  claims 1 , wherein the olefin copolymer has a degree of crystallinty of less than 25 mass % as determined by X-ray and differential scanning calorimetry. 
     
     
         7 . The composition as claimed in  claims 5 , wherein the olefin copolymer has a degree of crystallinty of less than 25 mass % as determined by X-ray and differential scanning calorimetry. 
     
     
         8 . The composition as claimed in  claim 1 , in the form of a marine diesel cylinder lubricant. 
     
     
         9 . The composition as claimed in  claim 7 , in the form of a marine diesel cylinder lubricant. 
     
     
         10 . The composition as claimed in  claim 1 , in the form of a trunk piston engine oil. 
     
     
         11 . The composition as claimed in  claim 7 , in the form of a trunk piston engine oil. 
     
     
         12 . 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. 
     
     
         13 . A method of lubricating a trunk piston marine diesel engine comprising supplying a composition as claimed in any of  claims 1  to the engine. 
     
     
         14 . 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 0.05 to 6 mass % of (B) a viscosity modifier in the form of an olefin copolymer. 
     
     
         15 . The method as claimed in  claim 14 , wherein (B) substantially replaces the brightstock so that the composition includes less than 0.5 mass % of brightstock. 
     
     
         16 . The method as claimed in  claim 14 , wherein (B) substantially replaces the brightstock so that the composition includes less than 0.1 mass % of brightstock. 
     
     
         17 . The method as claimed in  claim 16 , wherein (B) replaces the brightstock so that the composition is completely or substantially free from brightstock. 
     
     
         18 . The method as claimed in  claim 14 , wherein the two-stroke marine engine lubricating oil composition has a TBN of 40 to 100 mg KOH/g, as determined using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as determined using ASTM D2896. 
     
     
         19 . The method as claimed in  claim 15 , wherein the two-stroke marine engine lubricating oil composition has a TBN of 40 to 100 mg KOH/g, as determined using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as determined using ASTM D2896. 
     
     
         20 . The method as claimed in  claim 17 , wherein the two-stroke marine engine lubricating oil composition has a TBN of 40 to 100 mg KOH/g, as determined using ASTM D2896, or the four-stroke marine engine lubricating oil composition has a TBN of 25 to 60 mg KOH/g, as determined using ASTM D2896.