How often should an engine air filter be changed?

Updated: October 23, 2022
The engine air filter should be replaced if it's dirty or damaged, or every 20,000-25,000 miles depending on the driving conditions. If you have a turbocharged engine or often drive on unpaved roads, change the air filter more often.
The air filter should also be replaced every 3-4 years regardless of the mileage, as with age it becomes brittle and can tear apart. If in doubt, ask your repair shop to check the condition of the air filter during your next oil change service; it's easy to see if it's dirty.

Engine air filter in a carEngine air filter: New vs Dirty.
The air that enters your engine flows through the air filter. The engine air filter catches sand and other debris protecting your engine and helping it last longer. The air filter is installed inside the air filter box. It's made of pleated paper-like material. The air flows from the bottom up, so the dirt and larger objects are trapped in the box under the filter.

What happens when an engine air filter gets dirty? As the air filter gets dirty and gradually clogs up, it restricts the air flow into the engine. This adds strain on your engine, making it harder for it to "breathe." Due to increased vacuum, some dirt particles could be sucked through the filter and scratch the engine pistons and cylinder walls. For the same reason, the engine with a very dirty air filter may consume more oil. Having a clean air filter is even more important if you have a turbocharged engine, as it needs a lot more air when turbo is at full boost.
Symptoms of a dirty air filter include a lack of power on hard acceleration and at higher RPMs, although it's not that easy to notice. The gas mileage may drop a little. In extreme cases, the "Check Engine" warning light may illuminate on the dash.

The air filter is inspected during your regular oil changes. Your mechanic can check its condition and let you know if it needs to be replaced.
Engine air filter in a car The filter on the right is dirty after 24,000 miles.
If the filter looks clean, leave it; if it's very dirty, change it. Anything in between is a judgement call.

Some mechanics test the condition of the air filter by looking through it at the light source; if no light is visible through the filter, it must be replaced. For example, compare these two air filters in the photo. The filter on the right was changed one year ago, but the owner of this Honda drives over 24,000 miles a year. Now it looks dirty, so we have replaced it again.
Slightly dirty air filterSlightly dirty air filter
Dirty air filterDirty air filter
Extremely  dirty air filterVery dirty air filter
New and dirty air filtersNew vs dirty air filters

If you want to check it yourself, check your vehicle's owner's manual; as it has the engine compartment map. In some cars, to open an air filter box you will need some tools, like an 8-mm or 10-mm socket or a screwdriver.

Engine air filter in a carReplacing an air filter.
In other cars, the air filter box cover is held by a few clips. In most cars, checking or replacing an engine air filter is an easy job.

If you change your air filter yourself, make sure it fits properly and the air box is closed tight after the job is done. If the air filter box is not closed properly, the Check Engine light may come on. Whenever an air filter is replaced, it's a good idea to clean any debris that may have accumulated inside the air filter box.

Replacing an air filter in the repair shop is not very expensive: $10-$30 labor plus $19-$45 part.
Is it important to have an air filter replaced at a dealer or can a fast lube shop do the job? Replacing an air filter is fairly easy in most cars and can be done in any repair shop, however using a factory (OEM) part from a dealer will ensure that it fits properly. We have seen cheap filters that don't fit properly. If you opt for an aftermarket part, invest a little extra for a premium brand for better engine protection.
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Are washable air filters better? If it's a high-quality filter and is installed properly and cleaned regularly, it will work. However, we have seen problems related to washable filters or their installation. We also know cases where having a washable air filter caused some issues with the warranty coverage. Considering this, we recommend doing some research before and keeping the original OEM filter and the hardware if you do install a washable filter. The air filter is not an expensive part, but it does a very important job of protecting the engine. We prefer using OEM air filters.

Is it necessary to replace a cabin (pollen) filter whenever an engine air filter is replaced? It's not necessary, however if the engine air filter is dirty, the cabin filter is likely to be in the same condition.