How often does the air filter of an ordinary car be replaced?

It depends on the vehicle environment.

It is recommended to clean the air filter element every maintenance. If the dirt is serious, the replacement cycle should be shortened (for example, after the vehicle is cleaned, it can't be replaced until the maintenance time, and it may need to be replaced every 1000 km, because it runs slowly, but the actual working hours are long and the environment is bad). Generally 2-3 maintenance, it is recommended to replace the air filter element once. When choosing, even if the original accessories are used, the cost will not be too high, but it will greatly help to reduce the wear and tear of the engine.