Why are there so many different oil viscosities for car owners to choose from?
This is because every country, every car manufacturer, and every model will be equipped with different grades and different viscosities of oil according to its own car engine design characteristics, environmental emission requirements and other factors to meet and optimize the use of the car engine state. (The specific oil viscosity suitable for your model is listed in the "Car Maintenance Manual" that came with the car when you purchased the car. Check it carefully and it will be clear) The suitable oil viscosity is the primary condition for establishing an oil film on the friction surface. In order to prevent the wear of the contact area between the parts, the oil must have sufficient viscosity to ensure that an oil film can be formed in the moving parts at various operating temperatures. The viscosity of the engine oil is not the bigger the better. On the contrary, if the viscosity of the engine oil is too large or too small, it will have a certain degree of adverse effect on the car.
What will happen if the viscosity is too large?
1. Difficulty starting the engine at low temperature
The engine lubrication viscosity is too large, the flow is slow, the oil pressure is high, but the amount of oil passing through is not much, especially when starting at a low temperature, the oil cannot be replenished to the friction surface in time, and temporary dry friction or semi-fluid friction is most likely to occur at this time. And aggravate the wear of the parts.
2. The effective power of the engine is reduced
Due to the high viscosity of the oil, the frictional resistance of the friction surface of the parts increases. The friction area of ​​the friction parts in the automobile engine is very large. A layer of oil is covered on these surfaces. When the moving speed of the parts is very fast, even if the viscosity of the oil increases slightly, the loss of frictional power will increase a lot. In order to overcome the increased friction, it is necessary to consume more fuel. On the other hand, the viscosity of the oil is high, and the churning resistance of the crankshaft will increase when the crankshaft is running at high speed, so that the power loss inside the engine increases, which reduces the effective power of the engine.
3. Poor cooling effect
The higher the viscosity of the oil, the worse the fluidity, the slower the circulation speed, and the slower the heat is taken away from the friction surface, so the cooling effect is poor and the engine is easy to overheat.
4. Poor cleaning effect
The viscosity of the oil is high, the circulation speed of the oil is slow, and the number of times passing through the filter will be reduced, and the worn metal debris, carbon particles, dust and other impurities cannot be taken away from the friction surface in time, and the cleaning effect is poor.
What happens if the viscosity is too small?
1. The oil film is easily damaged
The oil viscosity is small, and it is difficult to form an oil film of sufficient thickness on the high-temperature friction surface. The oil film has poor bearing capacity and is easily damaged under load, so that the parts cannot be lubricated normally, which will increase wear.
2. The sealing effect is not good
The viscosity of the oil is small, the sealing effect is poor, and the cylinder is easy to leak air, which not only reduces the power, but also makes it easy for the exhaust gas to enter the crankcase, diluting and polluting the oil.
3. Increase oil consumption
The oil viscosity is small, the sealing performance is not good, and the evaporation loss is large. In this way, it is easy for the oil on the cylinder wall to enter the combustion chamber, causing the oil to burn, which not only increases the consumption of oil, but also causes incomplete combustion and increased carbon deposition in the combustion chamber.