What is the reason for the noise of cheap fuel engines?

If it is running-in, consider this reason. In addition, engine oil quality, three-way catalyst, etc. Will affect the sound. If you feel beyond the normal range, you'd better go to 4s for testing.

Development history

petrol

/kloc-in the 0/9th century, people didn't realize the importance of gasoline. At that time, kerosene was widely used for lighting. At that time, petroleum refining relied on a simple distillation process to separate components with different boiling points from petroleum. Kerosene has a high boiling point and is safe to use when igniting. It has become the main product of crude oil refining, while gasoline and other components are usually burned as fuel.

/kloc-in the middle and late 9th century, internal combustion engines using gasoline were successfully manufactured, and 1886 gasoline engines were successfully used as vehicle power. Therefore, the importance of gasoline is increasing day by day.