Marine engine lubrication

Abstract

Trunk piston marine engine lubrication, when the engine is fueled by heavy fuel oil, is effected by a composition of TBN in the range of 20 to 60 comprising a major amount of an oil of lubricating viscosity containing 50 mass % or more of a Group 1 basestock, and respective minor amounts of an overbased metal calcium alkyl salicylate detergent providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, and 0.1 to 10 mass %, based on the mass of the composition, of an oil-soluble linear alkyl-substituted phenol. Asphaltene precipitation in the lubricant, caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

1 . A trunk piston marine engine lubricating oil composition having a TBN in the range of 20 to 60 mg KOH/g, which composition comprises or is made by admixing an oil of lubricating viscosity, in a major amount, containing 50 mass % or more of a Group 1 basestock, and, in respective minor amounts:
 (A) an overbased calcium alkyl salicylate detergent providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, as determined by titration; and   (B) 0.1 to 10 mass % active ingredient, based on the mass of the composition, of an oil-soluble linear (straight chain) alkyl-substituted phenol.   
     
     
         2 . The composition as claimed in  claim 1  wherein (A) provides 50 to 80 mmol of calcium alkyl salicylate per kg of the composition. 
     
     
         3 . The composition as claimed in  claim 1  wherein the alkyl substituted phenol of (B) is monosubstituted with a linear alkyl group having 9 to 30 carbon atoms. 
     
     
         4 . The composition as claimed in  claim 1  wherein (B) is an alkylbenzenol. 
     
     
         5 . The composition as claimed in  claim 3  wherein (B) is an alkylbenzenol. 
     
     
         6 . The composition as claimed in  claim 4  wherein alkyl-substitution in the benzenol is in the 2-position or in the 4-position. 
     
     
         7 . The composition as claimed in  claim 5  wherein alkyl-substitution in the benzenol is in the 2-position or in the 4-position. 
     
     
         8 . The composition as claimed in  claim 1  wherein (B) is present in the range of 0.1 to less than 0.5 mass % of the mass of the composition. 
     
     
         9 . The composition as claimed in  claim 1  wherein (B) is present in the range of 0.2 to 10 mass % of the mass of the composition. 
     
     
         10 . The composition as claimed in  claim 1  wherein (A) is C 9  to C 30  alkyl-substituted. 
     
     
         11 . The composition as claimed in  claim 1  having a TBN in the range of 40 to 55 mg KOH/g. 
     
     
         12 . The composition as claimed in  claim 11  having a TBN in the range of 35 to 50 mg KOH/g. 
     
     
         13 . The composition as claimed in  claim 1  having a TBN of 45 to 55 mg KOH/g, wherein (A) provides up to 80 mmol of calcium alkyl salicylate per kg of the composition. 
     
     
         14 . The composition as claimed in  claim 1  having a TBN from 30 to less than 45 mg KOH/g, wherein (A) provides up to 70 mmol of calcium alkyl salicylate per kg of the composition. 
     
     
         15 . The composition as claimed in  claim 1  having a heavy fuel oil content. 
     
     
         16 . A method of operating a trunk piston medium-speed compression-ignited marine engine comprising
 (i) fueling the engine with a heavy fuel oil; and   (ii) lubricating the crankcase of the engine with a composition as defined in  claim 1 .   
     
     
         17 . A method of dispersing asphaltenes in a trunk piston marine lubricating oil composition during its lubrication of surfaces of the combustion chamber of a medium-speed compression-ignited marine engine and operation of the engine, which method comprises
 (i) providing a composition as defined in  claim 1 ;   (ii) providing the composition in the combustion chamber;   (iii) providing heavy fuel oil in the combustion chamber; and   (iv) combusting the heavy fuel oil in the combustion chamber.