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 a calcium alkyl salicylate detergent system providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, and 1 to 7 mass %, based on the mass of the composition, of an oil-soluble polyalkenyl-substituted carboxylic acid anhydride, wherein the or at least one polyalkenyl group is derived from a polyalkene having a number average molecular weight of from 200 to 3,000. Asphaltene precipitation in the lubricant, caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

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 a calcium alkyl salicylate detergent system providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, and 1 to 7 mass %, based on the mass of the composition, of an oil-soluble polyalkenyl-substituted carboxylic acid anhydride, wherein the or at least one polyalkenyl group is derived from a polyalkene having a number average molecular weight of from 200 to 3,000. Asphaltene precipitation in the lubricant, caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

Lubricating oil composition is provided. The composition includes several components including a base oil, a primary antioxidant including alkylated diphenylamines having an alkyl group derived from propylene tetramers, and a carboxylate detergent.

Lubricating oil composition is provided. The composition includes several components including a base oil, a primary antioxidant including alkylated diphenylamines having an alkyl group derived from propylene tetramers, and a carboxylate detergent.

A grease composition for vehicular hub unit bearings is provided, in which a base oil is a synthetic hydrocarbon oil having a kinematic viscosity at 40 C. of 25-50 mm.sup.2/s, a thickener is an alicyclic aliphatic diurea compound, based on a total mass of the composition, 0.1-5% by mass of a carboxylic acid-based corrosion inhibitor, 0.1-5% by mass of a carboxylic acid salt-based corrosion inhibitor, and 0.1-3% by mass of an amine salt of a fatty acid are contained, and a worked penetration is 220-270.

A grease composition for vehicular hub unit bearings is provided, in which a base oil is a synthetic hydrocarbon oil having a kinematic viscosity at 40 C. of 25-50 mm.sup.2/s, a thickener is an alicyclic aliphatic diurea compound, based on a total mass of the composition, 0.1-5% by mass of a carboxylic acid-based corrosion inhibitor, 0.1-5% by mass of a carboxylic acid salt-based corrosion inhibitor, and 0.1-3% by mass of an amine salt of a fatty acid are contained, and a worked penetration is 220-270.