How do I know if my engine air filter needs replacing?

Open the air filter box (usually a black plastic box with a clamp or clip on the driver's side engine bay) and pull out the filter. Hold it up to the light. If it's uniformly dark gray or brown, or you can't see light through it, replace it. A new filter is white or light gray. Visual inspection takes 30 seconds.

How often should an engine air filter be replaced?

Every 15,000–30,000 miles under normal conditions. If you drive on dusty roads, increase the frequency. Most cars specify 15,000–20,000 miles in the owner's manual. It's inexpensive enough that erring on the side of more frequent replacement is fine.

Does a dirty air filter really hurt fuel economy?

On modern fuel-injected cars, the engine's computer compensates somewhat for restricted airflow — so the fuel economy hit is smaller than it was on older carbureted cars. But a severely clogged filter will cause rough running and reduced power, and replacing it is so cheap ($15–$25) that there's no reason to delay.

Engine Air Filter

easy DIY~0.25h job

What it does

Your engine needs a precise mix of air and fuel to run. The engine air filter sits at the start of the air intake system, catching dust, pollen, and debris before they can reach the engine's cylinders and abrade the pistons and cylinder walls. It's like the air filter in your home HVAC — over time it collects so much debris that it restricts airflow. A severely clogged filter starves the engine for air, reducing power, worsening fuel economy, and (in extreme cases) causing rough running. The good news: replacing it is one of the cheapest and easiest maintenance items on any car.

Fix-vs-Skip Money Panel

DIY Cost

~$20

parts only

Shop Cost

~$45

parts + labor

Easy DIY~0.25h job

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Frequently asked questions

car maintenance — complete guide