The car engine is in the design phase, and the fuel used for the compression ratio is set. The compression ratio is a very important structural parameter of the engine, which indicates the volume of the gas at the beginning of the piston at the beginning of compression and the volume ratio of the gas volume at the end of the piston. In terms of power and economy, compression ratio should be bigger and better. The compression ratio is high, the power is good, the heat efficiency is high, the vehicle acceleration, the top speed of the car will be improved accordingly. However, the compression ratio of the gasoline engine is not too large due to the performance of the cylinder material and the vibration of gasoline combustion. In short, a high compression ratio USES a high grade fuel oil. The higher the fuel mark, the slower the oil will burn, and the lower the combustion detonation, the higher the compression ratio of the engine. On the contrary, the low-grade fuel combustion rate is faster, the combustion explosion is large, the engine compression is lower.