With the improvement of piston ring technology, now German cars have basically solved the problem of burning oil that costs people money. In the past two years, Japanese cars have repeatedly experienced the problem of increasing engine oil and emulsification. Especially in winter, the cap of the oil filler will show the texture of "milk cap", and the oil level will rise a lot. Now we will explain it to you in two parts: oil emulsification and oil increase!

Why does oil emulsify?

The direct reason for oil emulsification is that the oil is flooded. Where does the water come from? It is possible that the coolant leaks into the engine oil, but because these engines with problems are new engines, the possibility of poor sealing due to aging of the sealing gasket is small. After removing the coolant, there are roughly two sources of water in the engine: one is the high water content of the air inhaled by the intake system, and the second is the small amount of water generated after the combustion of gasoline.

Although most of the water vapor formed in the combustion process of the engine will flow out of the exhaust, a small amount of water vapor will still become a fish in the net! This is because it is impossible to ensure 100% sealing between the piston and the cylinder wall, so there will always be some high temperature gas containing water and gasoline flowing into the crankcase through the gap between the piston and the cylinder wall. This part of gas is called "blowby".

In order to evaporate water from the engine oil, there is a prerequisite, that is, the engine oil needs to reach the normal operating temperature of 100-120 ℃. However, when the vehicle is parked outside in the cold winter for one night, the temperature of the crankcase cannot be rapidly heated up like the cylinder in the burning state at all times. This will lead to a large temperature difference between the upper cylinder and the lower crankcase after the engine is cold started. Therefore, when the high-temperature water vapor generated by cylinder combustion flows into the cold crankcase below, the water vapor will form water droplets and mix into the engine oil, and because the engine oil temperature is too low to evaporate the water, the emulsification problem of engine oil will occur.

Emulsion inside the oil cap does not mean that the engine oil is emulsified.

Many car owners think that the emulsification on the inner surface of the engine oil cover means that the oil is emulsified, but it is not necessarily. The water in the engine generally exists in the form of water vapor. When the engine is working, it will rise to the top of the engine with the hot air flow, that is, the oil cap. Since one side of the oil cover is inside the engine and the other side is in contact with the outside air, there is a large internal and external temperature difference, so the water vapor will condense into water inside the oil cover, and the oil vapor will also condense into oil droplets here. Like a cup of warm water, when you open the lid, there will always be water droplets on the inner surface of the lid. When the water droplets on the inner surface of the oil cap combine with the oil droplets, an emulsion is formed, which is a normal phenomenon. Therefore, emulsification on the inner surface of the oil cap does not mean oil emulsification.

Why does the oil increase?

If you do not overfill when filling oil, but find that the oil level exceeds the upper limit of the dipstick scale after driving for a period of time, it means that there is a problem of "oil increase". The principle of oil increase and emulsification is not the same. Emulsification is the mixing of water in the oil, while oil increase is the mixing of gasoline in the oil.

So how does gasoline mix with engine oil? In fact, gasoline blends with engine oil all the time, which is the same as the high-temperature water vapor blowby just mentioned. The atomized gasoline that is not completely burned in the cylinder will also flow into the crankcase and blend with engine oil. However, because the content of gasoline in the blow-by gas is extremely low, it will not cause any negative impact on the engine oil and will not be noticed by everyone. In a cold winter, the increase of oil is visible to the naked eye, which is the "oil increase" problem that car owners need to be vigilant and will cause serious damage to the engine.

In low temperature environment (below 0 ℃), short distance driving (single driving ≤ 8km), it is difficult for the engine to reach the warm-up state, the gasoline in the engine oil is difficult to be discharged through the PCV cycle, and it is inevitable that the oil level will rise.

After experiencing the storm of oil increase in the previous two years, some joint ventures have accelerated the temperature rise of the cylinder wall by increasing the idle speed of the vehicle, thereby shortening the time of fuel injection to compensate for the poor gasoline atomization effect, so the problem of oil increase has been basically controlled. It's just that the speed and noise of many models become more annoying when they start cold in winter.

Why is the hybrid car in the disaster area?

This is because pure fuel vehicles can reach the normal operating temperature as long as the driving speed and time are enough. However, for hybrid vehicles, because the engine of the hybrid vehicle does not have idle running, and the engine is usually in the intermittent working state of starting and running for a while and then stopping when the vehicle is running, that is, the engine does not do idle work, so the heat generated by the engine is naturally very small.

混动发动机间歇式工作 

If it is in cold winter, especially in the case of urban low-speed congestion, the hybrid engine is often in the flameout state, it will also directly cause the water in the crankcase to be difficult to evaporate, thus accelerating the emulsification speed of oil.

More oil is harmful - what should I do?

What effect will oil level rise and oil emulsification have on the engine? I believe that the car owners are very concerned about this problem. The main functions of engine oil are cleaning, lubrication, heat dissipation, sealing, buffering and shock absorption, corrosion prevention, etc. Once gasoline is mixed with engine oil, it will greatly increase the formation speed of oil sludge, and no matter where the oil sludge is accumulated in the engine, it will cause the heat dissipation and lubrication performance of the engine to decline. More seriously, oil sludge is not a reversible reaction like oil emulsification, which means that it is difficult to eliminate oil sludge once it is generated, and it will only increase without decreasing in the oil, pile up more and more, and then stick to the inside of the engine, and will not even be discharged with the oil change.

The reason for the rise of the oil level is that the engine has been operating below the normal operating temperature for a long time. Therefore, the owner only needs to ensure that the engine can reach the normal operating temperature during driving. For current cars, it is not recommended to warm the car in place after cold start. Under this condition, the engine load is low, so the temperature rise is relatively slow, and the time for warm up is long. In addition, at this time, the amount of fuel injected by the engine is large, which aggravates the degree of oil dilution. So the correct way to warm up the car is to drive in gear after the car is started, but don't drive violently until the engine reaches the normal operating temperature.

Forced engine operation can greatly shorten the time required for engine warm-up.
The owner of the hybrid vehicle can shift to P gear and press the accelerator to force the engine to start after the cold start, or keep the accelerator depth slightly while driving to force the engine to run. These methods can make the engine warm up quickly. After warming up, drive normally.
The engine warm-up speed is also related to many factors, such as ambient temperature, oil fluidity, and so on. Therefore, in a low temperature environment, more attention should be paid to the temperature of the engine, and the use of low viscosity oil with good fluidity will also help to shorten the engine warm-up time.

It can be seen that behind the increase of engine oil, there is an unknown chain reaction This is also a good explanation for why the automobile manufacturers are not satisfied with the emulsification of oil cap, but are fully committed to the problem of oil increase. At the same time, this is also the main reason why more and more engines have started to turn to central injection in recent years.