Filters and Clean Air: Engine and Cabin Filters

The Two Filters Most Owners Forget

Your vehicle has one filter that protects the engine and another that protects you. Both are inexpensive, both are easy to check, and both are routinely skipped because they are not part of an oil change.

A clogged engine air filter makes the engine work harder for the same result. A clogged cabin filter means you are breathing whatever the filter is supposed to catch.

The Engine Air Filter

It sits in a plastic housing connected to the engine by a large tube. Its job is to stop dust, sand, and grit before they reach the cylinders, where they would act like sandpaper on the cylinder walls and piston rings.

• How to inspect it — Open the housing clips or screws, lift the filter out, and hold it up to a light. You should be able to see light through the pleats.
• Replace it when — It looks matted, has visible debris packed into the pleats, or light no longer passes through.
• Do not blow it out — Compressed air can tear the filter media and let grit through. If it is dirty, replace it.
• Never run without one — The filter is the engine’s only defense against abrasive dust.

The Cabin Air Filter

This filter cleans the air that enters through your vents, catching dust, pollen, exhaust particles, and mold spores. On most vehicles it lives behind the glovebox, though some are under the hood near the base of the windshield.

Replace it once a year, or sooner if airflow from the vents has weakened, the windows fog more easily than before, or you notice a musty smell when you turn on the fan.

Replacing Them Yourself

Both jobs are among the easiest DIY tasks on a modern car and usually take less than fifteen minutes each.

• Get the right part — Look up the filter for your exact vehicle rather than matching by size at the shelf.
• Engine filter — Release the clips or screws, note which way the old filter faced, wipe out the housing, seat the new filter, and close it back up.
• Cabin filter — Empty the glovebox, squeeze the sides or release the dampener so the box drops, pull the filter tray out, note the arrow direction, install the new filter, and reassemble.
• Check the airflow arrow — The arrow shows the direction air travels, not which way is up.

How Often to Replace Them

Check your owner’s manual for the intervals your manufacturer specifies, and write both filters into your maintenance log so you can see when they were last changed.

• Engine air filter — Roughly every 15,000 to 30,000 miles, and more often if you drive on gravel or dirt roads, in construction dust, or through wildfire smoke.
• Cabin air filter — Every 12,000 to 20,000 miles, or once a year in most climates. Twice a year if you have allergies or drive in heavy traffic daily.