Great Wall Xishi accelerator cleaning agent

This is commonly known as carbon deposition. If the estimate is correct, it should be that your additive is fake. Many of these additives on the market now simply don't work. I suggest you go to a regular car care shop to buy it. You can buy a bottle of engine cleaner to clean it the next time you change the oil. Don't worry about driving, it won't take long to have a problem.

Have fun!