Two-year-old car, washed the accelerator and changed the spark plug last month. Why does fuel consumption become very high?

There will be errors in the computer display. Have you actually calculated the fuel consumption yourself? Actually, you can do the math yourself first. Cleaning the throttle and replacing the spark plug will not lead to an increase in fuel consumption. If the actual fuel consumption is really high, it is recommended to check the fuel system of the vehicle. See if there is something wrong with the injector, and it won't close well after spraying. It will also lead to an increase in fuel consumption.