National regulations: The permissible moisture content in motor oil should be below 0.03%. When the moisture content exceeds 0.1%, additives, oxidants, clean dispersants, etc. in the engine oil will be lost, thereby accelerating the oil oxidation process. If there is too much water in the oil, the lubricity is poor and the viscosity is decreased. If the oil is light, the oil will deteriorate prematurely and the parts will rust. If the oil is heavy, the engine will hold the shaft and burn the tiles. So how do you distinguish oil and water? 1, the color method. The oil that meets the cleanliness is translucent in blue and brown in the oil. With water-containing oils, when the engine is running for a period of time, the oil is white and accompanied by foam. 2, combustion method. Heat the iron bar and put it in the engine oil. If there is a "click" sound, it means that there is more moisture in the engine oil. Or when the oil is injected into the test tube and the temperature is close to 80-100°C, a “click†sound is generated in the tube, indicating that the engine oil contains more water.