LUBRICATING OIL COMPOSITION

PROBLEM TO BE SOLVED: To provide a lubricating oil composition capable of enhancing lubrication performance in a diesel engine equipped with an exhaust gas recycling (EGR) unit. SOLUTION: This lubricating oil composition has a sulfur content of less than about 0.3 mass% and comprises a large quantity of an oil (a) of lubrication viscosity, a small amount of high-molecular weight polymer (b) comprising at least a copolymer (i) which is a copolymer of a hydrogenated polymer of a monovinyl aromatic hydrocarbon and a conjugated diene polymer and the hydrogenated polymer of a monovinyl aromatic hydrocarbon occupies at least about 20 mass% of the copolymer, an olefin copolymer (ii) containing alkyl or aryl amine or amide group, a nitrogen-containing heterocyclic group or an ester bond and/or a derivative (iii) of an acrylate having a dispersing group or an alkylacrylate copolymer, and a phenate detergent (c) which is a neutral and/or an over-based phenate detergent capable of providing to a lubrication oil composition at a ratio of about 6-about 50 mmol phenate surfactant per 1 kg of the final oil, and this lubricating oil composition contains in the lubrication oil composition a salicylate surfactant less than 1 mmol per 1 kg of the final oil. COPYRIGHT: (C)2011,JPO&INPIT