This paper focuses on the recent hot discussion on engine oil increase and engine oil emulsification. The causes of these phenomena and the corresponding solutions are expounded in principle.

Let's start with the increase in oil. The increase in engine oil must be caused by "impurities" mixed in the engine oil. According to the working principle of the engine, when the engine is working, the pressure of the combustion chamber will be as high as 20~30 atmospheres, and then a small part of fuel mixture and combustion products, mainly water vapor, will enter the crankcase through the movement gap between the piston ring and the cylinder wall. This is usually called crankcase blowby. Crankcase blowby is a phenomenon that exists in every engine. No matter what brand and large displacement engine, crankcase blowby will occur. The blow-by gas contains unburned fuel mixture, steam and exhaust gas. When the engine is running at low temperature, these "impurities" may become liquid and mix into the engine oil. In the long run, it will dilute the engine oil, reduce its performance and accelerate its oxidative deterioration. Therefore, the engine will be equipped with a forced crankcase ventilation system, referred to as PCV system.

When the engine works at high temperature, gasoline, exhaust gas and a small amount of water vapor mixed in the engine oil will evaporate and be separated by PCV and oil-gas separator, in which gasoline and water vapor will be introduced into the intake manifold and then enter the combustion chamber for secondary combustion. The oil vapor is led back to the crankcase, making the oil in a dynamic and stable state.

Further discussion on oil emulsification. Shuai Jin Shi, professor Tsinghua University and deputy director of the Combustion Energy Center of Tsinghua University, believes that the essence of oil emulsification is that water and oil are mixed to form a white emulsion.

There are two main factors in the appearance of engine oil emulsifying phenomenon: first, at low temperature, the water vapor in the crankcase condenses into water and penetrates into the engine oil; Second, ethanol gasoline is a mixture of ethanol and ordinary gasoline at the ratio of 1:9, which makes it easier to absorb water. The water brought in enters the cylinder, and it will be mixed with engine oil if it does not evaporate well.

Xie, chief technical expert and senior engineer of China Quality Certification Center, also mentioned ethanol gasoline. He believes that if ethanol gasoline is stored in the engine for a long time, oil-water separation may occur. Water does not participate in combustion, but it becomes steam when the engine does work. Some water vapor will be discharged with the exhaust gas, and some water vapor may be mixed into the engine oil, resulting in emulsifying phenomenon of the engine oil.

Don't worry if it's just oil cap emulsification. Experts in the industry have made it clear that the emulsification of the oil cover will not have a substantial impact on the performance of the car, and it is also a normal physical phenomenon under certain conditions. Because the fuel contains hydrogen, it will form high-temperature steam after combustion. If the vehicle is driven at low temperature, it will take a long time for the engine block to heat up. At this time, the high-temperature steam will contact with the cold engine block and liquefy into water, and the water will flow back to the oil pan. After repeated short-distance and low-speed driving at low temperature for a long time, more and more water will accumulate and mix with engine oil to form emulsion.

Whether the engine oil is increased or the engine oil cover is emulsifying phenomenon, increasing the engine temperature and promoting the evaporation of gasoline and water in the engine oil will be improved, such as keeping the habit of hot cars and running long distances and high speeds properly. However, it should be noted that the increase of engine oil and the emulsification of engine oil caused by other factors need to be repaired in time.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.