First, the bad habits of car owners: bad habits of using cars, improper maintenance of cars.

1. Bad driving habits: Including frequent short-distance driving, the engine does not reach sufficient operating temperature. During low temperature or short distance operation, moisture and fuel in crankcase did not evaporate completely, which resulted in emulsification and sludge formation. The engine starts and stops frequently and idles for a long time, which is easy to happen in traffic jam. If the engine is overheated, the oil will accelerate oxidation at high temperature.

2. Improper maintenance of automobiles: oil is not replaced after expiration. Owing to the deterioration of oil, oxidizing insoluble substances are formed at high temperature and sludge is formed. The oil should be kept clean and dry. No impurities and moisture can be brought in. When replacing the oil, the old oil should be discharged clean. Failure to do maintenance as required, automobiles should be regularly replaced by three filters to maintain a good engine internal environment. Do not use inferior air filtration, will lead to poor air filtration effect, impurities in the atmosphere into the oil, oil pollution, accelerating oil oxidation. When antifreeze cooling water enters the engine, it will cause the engine oil to become thicker, oxidize and produce acidic substances.

2. Poor quality of oil

The quality of oil also has its advantages and disadvantages. High quality oil has better base oil and detergent dispersant, better oxidation resistance and thermal stability, can better avoid sludge formation, and help to remove internal impurities. For vehicles with poor road conditions, frequent traffic jams and heavy loads, it is recommended to use higher quality oil.

3. PCV Valve Failure

The crankcase ventilation valve of the engine is responsible for balancing the pressure of the crankcase when the engine is running at high speed. When the crankcase ventilation valve fails or blockages, the water vapor or other harmful pollutants in the crankcase can not be discharged in time. After chemical reaction, the sludge will be produced, and a vicious circle will occur, and the sludge will become more and more serious.

IV. Use of inferior fuel

Low-quality fuel may contain some colloidal substances with high sulfur content, which bring acid substances to the engine oil during combustion, and acid substances lead to the oxidation and deterioration of the engine oil. Excessive fuel entering the oil may also produce asphaltene by-products with the oil.