In response to the generally shorter time required for replacement of domestic automotive engine oils,laboratory static experiments with different material containers and road tests with different vehicles were carried out to study the quality change of engine lubricating oils in low daily mileage driving condition and discuss the rationality of replacement oil for 6 months.The results show that the total acid number,kinematic viscosity and initial oxidation temperature of engine oils is changed only slightly in 7 groups of laboratory static tests lasting 6 months.After the vehicle road test for about 27 months with an average daily mileage of 11 km,the engine oil is in good condition and far from the oil change indexes.For less used vehicles,the oil change period can be extended appropriately,and even to four times or more.