When to Replace Your Lawn Mower Air Filter (And Why It Matters)

Your lawn mower's air filter might be small, but it plays a critical role in engine health. It prevents dirt, grass clippings, and debris from entering the engine — and when it gets clogged, problems follow.

A dirty air filter restricts airflow to the carburetor, which throws off the fuel-to-air ratio. The engine runs rich (too much fuel, not enough air), which causes black smoke, poor fuel economy, fouled spark plugs, and reduced power. Over time, a severely clogged filter can cause engine overheating.

Most manufacturers recommend checking your air filter every 25 hours of use and replacing it every season or every 100 hours — whichever comes first. If you mow in dusty conditions, check it more frequently.

There are two main types of small engine air filters. Paper element filters are the most common. They should be replaced when dirty — don't try to blow them out with compressed air, as this can damage the filter media and push dirt through. Foam pre-filters or standalone foam filters can be washed with warm soapy water, rinsed, squeezed dry (don't wring), and re-oiled with a light coat of engine oil.

To check your air filter, locate the air filter housing — usually a plastic cover held on by a screw or clip on the side of the engine. Remove the cover and pull out the filter. Hold it up to the light. If you can't see light through a paper filter, it's time to replace it. If a foam filter is visibly dirty or deteriorated, replace it.

A new air filter costs a few dollars and takes two minutes to install. It's one of the cheapest and easiest maintenance items on your mower, but neglecting it can lead to expensive engine damage. We stock filters for most common mower brands at the shop.