An air filter consistently clogged with oil is most likely the result of turning the mower over the wrong way when you work on the blades underneath the mower deck. If you turn the mower over with the air filter down, the engine oil will leak out and into the filter, clogging it.
A lawn mower’s air filter is usually located near the top of the engine and is encased within a metal or plastic shroud that is usually secured by a screw or with snap fittings.
The air filter in a Craftsman lawn mower with a 4.75 horsepower engine is on the left side of the mower body. Find it by looking for a black plastic casing that seems to be attached to the body of the mower. It will be secured with either screws or plastic clips, depending on which Craftsman lawn mower you have.
One may also ask, can you use a lawn mower without an air filter? It isn’t good for the lawn mower to keep running it with the filter removed, however, because the engine actively draws air through the intake port, and without the filter, the piston cylinder can be quickly contaminated by particles that can damage the piston seals.