1. The acid resistance of the engine oil and the ability to neutralize acidic substances deteriorate with long-term use, which makes the acid value of the engine oil increase significantly when the engine is working, causing acid corrosion to the engine and shortening the service life of the engine.

2. The viscosity characteristics of the engine oil become worse when used for a long time. At high and low temperatures, the viscosity changes greatly. Poor low-temperature start-up performance will prevent the oil from quickly reaching the gaps of the moving parts when the engine is started, resulting in wear of the parts. Similarly, a good lubricating oil film cannot be formed at high temperatures, so it cannot provide good protection for the engine.

3. The anti-oxidation of the oil used for a long time is very poor. When the engine is working, it is easy to produce a large amount of carbon deposits, colloids, sludge and other substances deposited in the engine, which may cause poor lubrication, increased device wear, increased fuel consumption, and reduced power , and even in severe cases, the oil passage will be blocked, resulting in the consequences of pulling the cylinder.