Talk about the problem of loud engine sound.

Basically it doesn't matter. Whether semi-synthetic or fully synthetic, the engine oil specification is 5W-30. This parameter is fixed and the viscosity of engine oil is basically the same. The difference is that the full synthesis is more stable, the service life is longer and the engine protection is relatively better. But in the normal service life, it can meet the requirements of normal use, so it is said that the semi-synthesis is changed every six months.