There are two aspects to be considered in the selection of engine oil: one is the brand of engine oil: 1, and the other is the grade of engine oil. Please carefully check the oil grade used in your car and choose it strictly according to the regulations. 2. The choice of engine oil brand must consider the environmental temperature in this area. The area south of the Yangtze River can use 10- 15W-40 engine oil all the year round; 3. Choose 10- 15W-40 engine oil in the northeast in summer and 0-5W-30 or 40 engine oil in winter; 4. The smaller the viscosity of engine oil, the thinner the engine oil and the greater the mechanical wear. The purpose of low viscosity of engine oil is to facilitate starting. After the engine starting temperature comes up, the viscosity is still good for the machine! Therefore, under the condition of ensuring the normal start of the engine, the greater the viscosity of the engine oil, the better; We have a famous saying in car maintenance: save fuel, save fuel. This is the contradiction of oil selection. When selecting engine oil, we must adhere to the principle of "saving shaft".