You Need to Change Your Car’s Engine Air Filter

Engine air filter replacement guide highlights:

  • The engine air filter keeps dirt and other junk from contaminating your car’s engine
  • A clogged, dirty air filter can reduce your engine’s performance, damage your spark plugs, as well as cause rough idling, misfires, and even backfires
  • A new filter usually costs no more than $40 and installing it only takes a few minutes

I get it, it’s easy for your car’s simpler maintenance needs to slip into ‘worry about it later’ territory. And many times, the engine air filter is one of them. But as with some other oft-deferred tasks, not changing your car’s air filter regularly can cause a variety of problems. Fortunately, as this guide will explain, this is one maintenance job even beginners can easily tackle.

What does the air filter in your engine do?

An orange-and-yellow engine air filter being assembled in Mann+Hummel's factory
An engine air filter being assembled | Marijan Murat/picture alliance via Getty Images

Just like humans, internal-combustion engines don’t do well when they breathe in dirty air. That’s why cars have cabin air filters to grab dirt, soot, and other things before they enter the interior. And that’s why engines have their own air filters, too.

As your car’s engine runs, its throttle body (or bodies) is constantly regulating the flow of air from the intake. But before any air gets sucked into the intake, it must pass through the engine air filter. This traps everything from tiny dust particles to leaves and bugs, ensuring only clean air enters the engine. That way, nothing fouls up the finely tuned concert that is internal combustion.

Most engine air filters are made of pleated paper or cardboard with square rubber or plastic frames. The pleating vastly boosts the filter’s surface area, which improves airflow and lets the media catch more airborne crud. And the frame both keeps the filter material organized and acts as a sealing gasket. Some filters also have metal mesh for extra rigidity.

High-performance engine air filters, though, go several steps further. These filters ditch the paper for cotton gauze, which doesn’t restrict airflow as much. With more air, your engine responds better and makes more power, especially if it’s turbocharged or supercharged. Some also don’t think it’s hip to be square, opting instead for another shape that provides better airflow. But because cotton gauze can’t stop contaminants as well as paper, these high-performance filters use oil to pick up the slack.

What are the symptoms of a dirty engine air filter?

A 1999 Mazda MX-5 Miata's dirty aftermarket K&N high-performance air filter in the engine bay
1999 Mazda MX-5 Miata’s aftermarket K&N high-performance engine air filter | Matthew Skwarczek, MotorBiscuit

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On that note, much like the oil filter, your car’s air filter can only hold so much gunk. And even the best modern engines can only compensate so much for dirty air filters. So, eventually, clogged-up air filters start causing problems.

Initially, dirty air filters just sap some engine power. As a result, your car won’t accelerate as quickly, and you’ll have to push the gas pedal further to the floor. You’ll therefore also experience a drop in fuel efficiency. But this is often subtle, especially if you have an older car. Don’t worry, though, the more obvious signs come soon after.

If your engine air filter is especially dirty, it might prevent your car from keeping its air-to-fuel ratio under control. At which point, it can start idling roughly, make odd noises, and/or start misfiring, CarBibles explains. In extreme cases, it can even backfire, causing flames or black smoke to shoot from the exhaust. Filthy filters also wreak havoc on your spark plugs and create a strong fuel smell. And of course, your Check Engine Light might come on.

How often should you change your car’s engine air filter?

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Some claim you should change your car’s air filter every time you change the oil. But like the 3K-mile oil change, while that might’ve been accurate once, it’s not anymore.

As with the oil change interval, the air filter replacement schedule varies from car to car. Also, it changes based on where you drive. If there’s a lot of sand in your air, you’ll need to change the air filter more frequently.

A good general rule, though, is to change the filter every three years or 30,000 miles. And if your commute looks like Mad Max: Fury Road, shorten that to 15,000 miles. But check your owner’s manual to make sure. Also, if you check the filter and it looks truly filthy, you might want to consider changing it ASAP.

How do you change it?

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Changing your engine air filter is even easier than changing an oil filter. Unless you have a reusable one, the hardest part might be finding it. And even that’s fairly simple.

Just trace the air intake back from the engine until you reach the end. Usually, you’ll find the filter there in a plastic or metal box. Some small cars, though, might put that box in an interesting spot. My 500 Abarth’s engine air filter box, for example, is on top of the engine under what looks like the engine cover.

Regardless, once you find the air filter box, you can usually open it with a screwdriver or a socket wrench. Then, just replace the old filter with the new one and bolt everything back together. It literally takes a few minutes.

If you have a reusable engine air filter, though, as my old NB Miata did, you have a few more steps ahead of you. After removing the filter from the intake, you’ll have to wash and dry it. Then, you’ll have to reapply the oil that helps trap debris. And only once that soaks into the filter media can you re-install it on your air intake.

How much does a new one cost?

Two car mechanics in a garage compare a stock white (right) and high-performance red engine air filter
Two car mechanics compare stock (right) and high-performance engine air filters | Jack Milton/Portland Press Herald via Getty Images

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As with other parts, engine air filter prices vary based on your car’s make and model. But unless you’re hunting for a high-performance reusable one, they’re pretty cheap. A new filter for my 500 Abarth, for example, generally costs $30-$40. And even the air filter for something like a Porsche 911 is only slightly more expensive.

Also, while reusable filters cost more initially, their cleaning kits usually cost less than new disposable filters. The K&N cleaning kit for my NB, for example, only cost $20.

And that’s everything you need to know about changing your car’s engine air filter.

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