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.

Abstract: Two-stroke cross-head marine compression-ignited engine system lubrication is effected by a composition comprising a major amount of an oil of lubricating viscosity containing at least 50 mass % of a basestock containing greater than or equal to 90% saturates and less than or equal to 0.03% sulphur or a mixture thereof, and respective minor amounts of an oil-soluble overbased metal alkyl salicylate detergent and an oil-soluble polyalkenyl-substituted carboxylic acid anhydride or an oil-soluble alkylated phenol. The presence of the anhydride or the phenol improves asphaltene dispersency in the lubricant.