When Last / how often

How often should I change my cabin air filter?

Short answer

Every 15,000–30,000 miles (24,000–48,000 km), or about once a year. Once a year suits most drivers; make it twice a year if you sit in city traffic, drive dusty or unpaved roads, or have hay fever.

This is the filter for the air you breathe, not the air the engine breathes

Cars have two air filters and they are unrelated. The engine air filter protects the intake. The cabin air filter sits in the ventilation path, usually behind the glovebox or under the windscreen scuttle, and cleans the air coming out of the vents at your face.

Because the consequence of a dirty one is comfort rather than mechanical damage, it is the single most commonly skipped service item on a car — and the one you notice most once it is done.

What shortens the interval

  • Stop-and-go city traffic — you are drawing in the exhaust of the car in front, and the interval is really about hours of fan running, not distance
  • Unpaved roads, construction, or agricultural dust
  • Heavy pollen seasons, if anyone in the car has hay fever or asthma
  • Parking under trees, which packs the intake with leaf litter and seeds
  • A car that spends most of the year with air conditioning running, since the filter sits upstream of a damp evaporator

How to tell it is due

  • Airflow from the vents is weaker than it used to be at the same fan speed, and the fan is audibly working harder
  • A musty or sour smell for the first minute after you turn the fan on
  • The windscreen demists more slowly than it did
  • Visible debris — leaves, seeds, insects — when you pull it out
  • The definitive test: pull the old one and hold it beside a new one. The colour difference settles the argument in two seconds

Doing it yourself

On most cars this is a ten-minute job with no tools or with one screwdriver: empty the glovebox, release a damper or two clips, drop the tray, slide the filter out. There is an arrow on the frame showing airflow direction — it almost always points down. Note the direction of the old one before it comes out.

If you want the version that also handles the musty smell, an activated-carbon filter costs a little more and absorbs odours as well as particles. It does not change the interval.

So when did you last do it?

The interval is once a year for most people. Which means the only thing standing between you and getting this right is remembering whether last time was this spring or the spring before — and the honest answer, for almost everybody, is that it was longer ago than they think.

A filter you replace on a remembered date is a filter you replace roughly every three years. Write the date down once and the guessing stops.

Track days since “Cabin air filter”

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