Especially in recent years, with the tightening of environmental protection regulations and strict emission requirements, more efficient in-cylinder direct injection engines have become popular in the industry, and the increase of oil will always become a "seasonal" problem of automobile quality complaints every winter.
Q 1: What is the increase of oil?
A: Some people think that adding engine oil is better than burning engine oil. This is actually a very wrong concept.
For cars, engine oil is equivalent to human blood and plays an irreplaceable role in protecting engines. Increased oil is also called excessive dilution of oil. Essentially, the incompletely burned fuel in the combustion chamber is mixed with the engine oil, which leads to the deterioration of the engine oil.
A paper "Study on the Influence of No.93 Motor Gasoline on the Performance of Gasoline Engine Oil" by Lanzhou Lubricating Oil R&D Center of China Petroleum pointed out that when the content of No.93 gasoline in engine oil reaches 5%, the kinematic viscosity at 100℃ is only 54.4% of that of new oil. It is suggested that the gasoline content in engine oil should not exceed 10%.
The increase of gasoline content will lead to the decrease of oil lubrication effect, cylinder wear and even serious damage to the engine.
Q2: Why does oil increase?
Answer: It is an inevitable phenomenon for engines with direct injection technology in cylinder.
The combustion chamber of the engine is not absolutely isolated from the crankcase. When the engine is running, oil lubricates the piston and the cylinder wall on the crankshaft side of the piston, while gasoline does work in the combustion chamber on the other side of the piston. The gap is just the piston ring on the piston.
However, the side injection type that Japanese car companies like to use is prone to fuel spraying on the cylinder wall, wetting the cylinder wall and incomplete combustion. During the movement of the piston, the fuel will flow into the engine oil on one side of the crankshaft along the cylinder wall, resulting in dilution of the engine oil.
In addition, the high-temperature gas in the combustion chamber will inevitably blow into the crankcase, and will also bring gasoline and water vapor into the engine oil.
Q3: Why is it easy to increase the oil in winter?
A: In fact, there are mature solutions to the increase of oil caused by wet wall of oil injection and blowby in combustion chamber. Crankcase forced ventilation system is to solve these problems.
When the engine works normally, the temperature of the oil is about 90 degrees. After the fuel entering the crankcase evaporates, it is introduced into the intake manifold through the crankcase forced ventilation system and re-enters the combustion chamber for combustion, while the oil returns to the oil pan.
Under normal working conditions, the crankcase forced ventilation system can ensure that the engine oil will not be mixed with too much fuel and ensure the quality of the engine oil.
However, when the speed of fuel dissolving in engine oil exceeds the speed of fuel volatilization in engine oil, the problem of increasing engine oil will occur. Cold weather, cold start and short trip are more likely to lead to such problems.
20 18 A paper from the Technical Center of Dongfeng Motor Company pointed out that for in-cylinder direct injection engines, cold weather will inevitably lead to lower fuel injection temperature in the combustion chamber during cold start, which will make the fuel on the cylinder wall volatilize less. In addition, fuel is easy to burn incompletely at low temperature, and these fuels will enter the crankcase.
At this time, the oil temperature in the oil pan is also low, and the fuel evaporation efficiency is not high. In this way, the dissolution rate of fuel is faster than the evaporation rate, which leads to the problem of increasing engine oil.
However, even in cold weather, you only need to drive a car. When the engine temperature rises to the normal working level, the fuel in the engine oil will be naturally discharged through the crankcase forced ventilation system, and the engine oil will return to the normal level.
However, if it is in cold weather and works for a long time under short-distance working conditions, and the car stops without sufficient preheating, the oil in the oil pan will always be lower than the normal working temperature, and the fuel will not evaporate from the oil. After a period of accumulation, it will eventually lead to a significant increase in oil.
Q4: Why is there an oil emulsifying phenomenon?
Answer: Oil emulsification refers to the mixing of oil with other liquids, and the oil becomes emulsified, especially the white foam or milky yellow foam on the oil cover and cylinder head cover. The emulsification problem of engine oil is generally that the engine oil is mixed with incompatible liquids, such as water, alcohol and antifreeze. And an emulsion is formed during the intense stirring of the crankshaft.
Emulsification of engine oil will not only corrode engine parts, but also reduce the strength of lubricating oil film, and even cause engine damage due to wear.
The common cause of oil emulsification is the cracking of the heat exchanger, because water leakage causes antifreeze or water to enter the crankcase.
Another reason is that when the engine is working, the water vapor in the air sucked into the combustion chamber will enter the crankcase from the gap between the cylinder wall and the piston with the engine working, which will also cause water to mix into the engine oil.
Q5: Why is the emulsification problem of oil filling machine easy to occur in winter and spring?
A: In the winter and spring of this year, many people reported that there was an oil emulsification problem at the fuel filler, so they were very worried. But in fact, the problem of oil emulsification has always existed in winter, and it can even be said to be a normal phenomenon.
In the 20 15 paper "Emulsification principle of engine oil in winter and its influence on engine", the statistics of 47 private cars in Harbin show that there are 34 cars with fuel filler caps and engine oil emulsifying phenomenon.
This paper also explains the appearance of oil emulsifying phenomenon in the filler cap.
When the car runs for a short distance, the engine stops running when the temperature is low. Because the wall of plastic filler cap is thin, compared with cylinder block, cylinder head and oil pan, the filler cap has the worst heat insulation, so the cooling speed is the fastest. After the engine stops running, the steam escaping from the combustion chamber to the crankcase will condense into water at the lowest temperature, so the oil emulsification problem of the fuel filler cap appears.
When the engine is running normally, the condensed water quickly evaporates and is discharged from the crankcase through the crankshaft ventilation system. Cars with long mileage will not have such problems.
Q6: Hybrid vehicles are more likely to be emulsified with fuel and engine oil?
A: With the increase of hybrid cars in the market, many hybrid car owners find that hybrid cars are more prone to oil filler, so they are worried. Actually, this is a normal phenomenon.
Compared with fuel vehicles, hybrid vehicles are facing more extreme working conditions. The working logic of many hybrid cars is to use the motor to drive at a low speed, and wait until the power drops to a certain extent before starting the engine to charge. Therefore, under the working condition of short-distance driving, the engine of hybrid electric vehicle has been working intermittently, resulting in the oil temperature being lower than that of fuel vehicle.
Condensed water is produced, but it has not been able to evaporate the water in the engine oil and discharge it through the crankshaft ventilation system, which also magnifies the problem of condensed water in hybrid vehicles.
In fact, in the owner's complaint, it was also found that the engine oil did not deteriorate, but emulsifying phenomenon was found at the engine oil port, which was in line with the emulsification of the engine oil cover due to condensed water in winter.
I believe that as the weather gets warmer, people will start social activities again, and the problem of seasonal oil emulsification will soon disappear.
abstract
The increase of engine oil and the emulsification of engine oil are both important problems affecting the life and driving safety of automobiles, which must be paid attention to. For consumers, even if there is a problem with the vehicle due to weather, car habits and other reasons, and it does not affect the safety of use, it will guide consumers to travel with peace of mind. Manufacturers should follow up in time.
Of course, if the problem of oil increase and oil emulsification still occurs after long-term use or warmer weather, it must be a car failure or other problems. The owner must contact 4S shops and manufacturers as soon as possible to further investigate the problem. I believe that manufacturers will also pay attention to this point, check the problem as soon as possible, and make the car owners safer and more secure.
This article comes from car home, the author of the car manufacturer, and does not represent car home's position.