The engine needs to draw in a large amount of air to operate. The air contains dust and particulate matter. Once these substances enter the cylinder, they will become "abrasives", accelerating the wear of the piston rings and cylinder liners. The air filter is like a "mask" that protects the engine.
If not replaced regularly: A clogged air filter will increase intake resistance, resulting in insufficient engine intake, incomplete combustion, reduced power and increased fuel consumption. What's more serious is that once the filter element is damaged or not sealed tightly, dust will directly enter the engine, causing severe premature wear.