Two filters, both usually changed without a single tool, and both marked up two or three times at a shop.
They do different jobs. The engine air filter cleans the air the engine breathes. The cabin air filter cleans the air you breathe, through the vents. Neither is difficult, and a shop charging $75 to fit a $15 part is one of the most common small upsells there is.
- Time: 5–15 minutes each
- Difficulty: beginner — often no tools at all
- Saves: $15–$70 per filter
Buying the right ones
Give the parts counter your year, make, model and engine, or look them up online the same way. Engine filters run $10 to $30, cabin filters $10 to $30. Cabin filters also come in a charcoal version for a few dollars more, which helps with smells and traffic fumes and is worth it if you sit in traffic.
Buy both at once. You are already going to the store, and they are usually due at similar intervals.
The engine air filter
- Engine off and cool. Open the hood.
- Find the airbox. A big black plastic box, usually off to one side, with a fat flexible tube running from it toward the engine. It is one of the most obvious things under there once you know what you are looking for.
- Open it. Most have metal spring clips you flip with your fingers. Some use four screws, usually Phillips or an 8 mm or 10 mm socket. A few have a lid that lifts straight off once the clips are released.
- Note which way the old one sits — take a photo — and lift it out. It is a rectangular or round pleated panel, usually with a rubber edge.
- Wipe out any leaves and grit in the bottom of the box with a rag. Do not blow it toward the engine side.
- Drop the new one in the same orientation, rubber edge seating properly all the way round.
- Close the lid and refasten every clip or screw. Make sure the lid is properly seated — a lid that is not sealed lets unfiltered air past the filter entirely.
When to change it: most manufacturers say every 15,000 to 30,000 miles. Check the manual. If you drive gravel roads or dusty sites, sooner.
The cabin air filter
Behind the glovebox on most cars. Occasionally under the dash on the passenger side, or under the hood at the base of the windscreen. Search your year and model plus “cabin air filter location” if it is not obvious — there is a video for essentially every car ever made.
- Empty the glovebox.
- Release it so it swings right down. Usually there are stops on each side you squeeze inward, or a damper arm on one side you unclip. It feels like you are breaking it. You are not — it is designed to do this.
- Behind it is a plastic cover with clips or tabs. Pop it off.
- Slide the old filter out. Have a bag ready — they come out full of leaves and grit. Note the small airflow arrow printed on its edge.
- Slide the new one in with the arrow pointing the same way. Almost always downward, toward the floor, but copy what came out.
- Cover back on, glovebox back up.
When to change it: every 15,000 to 25,000 miles, or whenever the vents smell musty or the fan seems weak. This is the fix for a car that smells like a damp basement.
The dirty filter trick
Worth knowing, because these two filters are the classic prop. A service advisor appears holding a filthy filter and asks if you would like it replaced today for $75.
Sometimes it is genuinely yours and genuinely due. Sometimes the filter lives on a shelf. And an engine air filter that looks grey and dusty is often still perfectly serviceable — they are supposed to catch dirt. The honest test is mileage since it was last changed, not how it photographs.
Now that you know both are ten-minute jobs with a $15 part, “no thanks, I’ll do it myself” is an easy sentence to say.
The mistakes that catch people
- Fitting the cabin filter upside down. Follow the arrow.
- Not seating the airbox lid properly, or leaving a clip undone. You will hear it as a whistle or a louder engine.
- Buying by guesswork. Filters that look similar are often a few millimetres out and will not seal.
- Cleaning and reusing a paper filter. Tapping the loose dust out buys you a little time. It is not a substitute for a new one.
Information only, not professional advice. Work on your own vehicle is at your own risk. See the disclaimer.