There are all kinds of automobile oils, and the higher the type, the more viscous the oil will be. Moreover, cars leave the factory with fixed types, and many car models have different oils.
For example, when the engine is designed, the oil is set at 20. With the right engine oil, you will naturally run more briskly. If the oil is added at 40, the oil will be thicker. When the engine is doing work, it will have considerable power to overcome the resistance caused by engine oil, and the fuel consumption will naturally increase.
But 20% engine oil is rare in the market. 4S stores are basically 30, 40, and most of them are 40. When maintaining, few people know what viscosity oil should be added, and they have not read the instruction manual of the car. Often they just care about the brand and don't care about the oil parameters.
In addition, there is a price gap between different types of engine oils, especially in synthetic engine oil, with a gap of 40-50. Therefore, under this condition, 4S stores and repair departments rarely use the more expensive No.20 engine oil.
If the oil does not match, it will increase the internal resistance load of the engine and some parts will be damaged in advance. Therefore, in this market environment, we must read the instruction manual of the car, which contains engine oil and maintenance. Oil maintenance is all in it.