Professor Yao Chunde talked about three reasons for the increase of engine oil, one is that the metering state of engine oil is inconsistent, the other is that gasoline seeps into engine oil, and the third is that water enters engine oil. Let's take a closer look.
First of all, the first reason is that the measurement state is inconsistent. The oil density is different before and after hot car. If you measure after the hot car and find that the oil has increased, first make sure that your car has just been maintained. It may be that the car is in a cold state during maintenance, and the oil quantity seems normal at this time. But after the hot car, the density of the oil becomes smaller and sometimes it expands, so it seems that the oil level is higher. In this case, the increase of oil quantity is not a big problem.
Two or three reasons, let's talk about it together. If you understand the working principle of the engine, you will understand everything. When the four-stroke engine is running, the communication between the combustion chamber and the crankcase should be avoided as far as possible, and the piston ring is generally used as the seal between them. However, nothing is absolute, and such a seal cannot guarantee that the isolation effect of 100% can be achieved under any circumstances.
When the engine is working, some combustible mixture and combustion products will still escape into the crankcase through the movement gap between the piston ring and the cylinder. This part of gas is crankcase blowby, and its main components are hydrocarbons, water vapor, mixed gas and nitrogen oxides. Water vapor and gas mixture which are easily condensed by crankcase blowby will condense and mix with engine oil. In addition, when the engine works in a low temperature environment, some liquid fuel will directly enter the crankcase and mix with the engine oil.
These two sources are the main reasons for the increase of oil under normal circumstances. The situation of turbocharged direct injection engine is the most serious, because the larger in-cylinder pressure and the fuel directly injected into the cylinder make the wet wall phenomenon of turbocharged engine more serious, and more liquid gasoline will flow into the crankcase.
However, engineers are not helpless, because there is such a situation, so when designing a four-stroke internal combustion engine, a forced crankcase ventilation system, referred to as PCV system, will be introduced. The function of PCV system is to re-introduce this part of crankcase blowby into combustion chamber for combustion. Liquid fuel and water vapor dissolved in engine oil will evaporate again with the increase of engine oil temperature and enter the PCV system for consumption.
The rise in oil mentioned above is an extreme situation. In fact, during the normal operation of the engine, only a small amount of water vapor and liquefied gas are actually mixed in the crankcase, and few impurities will not affect the lubricating performance of the engine oil. In addition, the current engine oil technology has improved a lot, and the wear resistance and oxidation resistance have been greatly improved. As long as it is maintained in a stable state, it will not have any substantial impact.
What should you do if you find that your car has a slight increase in fuel? Professor Yao Chunde suggested that everyone should run more highways, which proved to be very effective.
My friend drives a Toyota car, and he also followed suit to test the oil condition. Unfortunately, his car also showed a slight increase in fuel, and he always wanted to go to the 4S test. I suggested that he drive to the highway and run twice. Later, when their company resumed work, he drove from Shenyang to Beijing. As a result, the oil problem disappeared after the test.
In fact, the reason for the increase in engine oil in his car is the same as everyone else, and it is related to the habit of using cars with high frequency and short distance. There is no need to panic in this case. Just change the car habits appropriately and occasionally run to the high speed, so don't worry too much, because no car has been exposed to quality problems so far.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.