A gas engine lubricating oil composition having a boron content of more than 95 ppm, the gas engine lubricating oil composition comprising: a major amount of a lubricating oil having a viscosity index of 80 to 120, and including at least 90 mass percent of saturates and 0.03 mass percent or less of sulphur; and at least one metal detergent.The gas engine lubricating oil composition exhibits improved oxidation and reduced deposit formation.