Disclosed is a lubricating oil composition comprising, as indispensable components, (A) a synthetic hydrocarbon lubricating oil, (B) a load-withstanding additive and (C) a liquid modified ethylene/.alpha.-olefin random copolymer. In this lubricating oil composition, the load-withstanding oil is homogeneously and stably incorporated. This lubricating oil is significant in that the poor compatibity with a load-withstanding additive, which is the defect of synthetic hydrocarbon lubricating oils, is effectively overcome.