It’s easy to tell when your windshield wipers need to be replaced because the evidence is right in front of you. Similarly, a dirty cabin air filter might release unpleasant odors or block air from flowing through the vents. An engine air filter that needs to be replaced, however, isn’t so obvious.
What Does the Engine Air Filter Do?
The air filter restricts air flow into the engine slightly, straining out dust and dirt. For every gallon of fuel injected, some 10,400 gallons of air flow through the filter to oxidize it. Over the recommended 15,000-mile air filter change interval, the average 25-mpg air filter will clean about 6.2 million gallons of air. That’s a lot of dust, pollen, soot, dirt, sand, bugs and other particles. Air filters are essential because without them, these contaminants would increase internal engine wear or foul spark plugs and fuel injectors.
When to Replace Your Air Filter
With proper maintenance, engines can last upwards of 500,000 miles, and some last over a million miles. To ensure your engine is clean and reliable, you need to change the air filter before it clogs or collapses. If a dirty air filter impacts performance or engine-starting, it should have been replaced a long time ago.
In cars with modern fuel-injected engines, a dirty air filter won’t activate the check engine light. But for some diesel-powered vehicles, a pressure differential sensor is the best indicator of when to replace the air filter. Additionally, if the filter indicator comes on or you see dirt in the filter’s folds, replace it.
Otherwise, you should replace it according to the automaker’s specifications in your car’s owners manual, usually somewhere between 12,000 to 30,000 miles. If you live in an area with dusty roads or heavy traffic, you may need to check and change your air filter more often.
How to Change Your Engine Air Filter
Fortunately, changing your engine air filter doesn’t require any special tools — just a screwdriver or nut driver at most.
1. Find the Air Filter Box: There are a few ways air filters can be secured in vehicles:
- Round filters: These are usually found on older cars, especially carbureted and early throttle-body-injection engines. Mounted right on top, these filters are usually held by a wing nut or latches.
- Conical filters: These are usually mounted inside a larger section of the air intake tube and held closed by a latch.
- Panel filters: The most common light vehicle air filter is a rectangular panel filter, inside an air filter box secured by bolts or latches.
2. Remove the Old Filter: Open the clips on the air filter box, remove the plastic cover and take out the dirty filter.
3. Clean the Box: While you’re there, inspect the air filter box and clean it if it looks dirty.
4. Secure the New Filter: Pop the new filter in, and close the box, making sure it’s sealed. Otherwise, airborne contaminants could be drawn into the engine, leading to accelerated wear.
It’s a good idea to write the date and your vehicle’s current mileage on the new filter. That way, you’ll know whether you need to replace it the next time you remember to check the air filter box.
Check out all the air filters available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on engine air filters, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.
Photo courtesy of Benjamin Jerew.
Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.