How Often Should You Replace Your Engine Air Filter?

How Often Should You Replace Your Engine Air Filter?
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Your car’s engine relies on three things to run: fuel, air and an ignition source. The air filter is an essential part of this equation, and knowing how often to change your engine air filter is a key part of vehicle maintenance. The good news is that changing it yourself is easy.

What is an engine air filter?

The air filter keeps dust, pollen and debris from entering your car’s engine. Without the air filter, your fuel system would get jammed with contaminants that damage the engine. Older air filters were a pleated paper design. Newer filters use a cloth or foam medium to trap debris.

The air filter can trap particles as tiny as a couple of microns, providing protection for the engine and fuel system. On older vehicles, the filter was inside a large, round metal housing on top of the carburetor, with a snorkel that allowed air to enter.

Newer cars have a hose that’s four or five inches, drawing air from the grille area and directing it back to the fuel injection’s throttle body. The air filter is located in a box, usually close to the intake at the grille. Some cars have a square or rectangular air filter frame, while others have a conical filter. The filter box lid is usually held on with plastic snaps or a bail, making the filter easy to access.

At a ratio of about 2,461 gallons of air for every 0.3 gallons of fuel, the air filter processes a huge volume of air. The filter has to do an effective job of preventing junk from entering the engine. At the same time, the filter can’t be so restrictive that it impedes air flow.

Engine air filter vs. cabin air filter

Since the late 1990s, carmakers equipped most vehicles with two air filters: one for the passenger compartment and one for the engine.The two filters serve different purposes, so clearing up any confusion about which is which is helpful.

The engine air filter is mounted under the hood, toward the front of the engine. Its job is to keep debris out of the engine. The cabin air filter, on the other hand, is often mounted behind the glovebox. It is designed to keep dust and allergens out of the vehicle’s HVAC system where they may cause problems for passengers.

The cabin air filter is typically changed every 12,000-30,000 miles, although sometimes more frequently if you’re in a heavily polluted area or regularly drive on dusty roads. Signs of needing to change the cabin air filter can include:

  • Allergic reactions or other respiratory problems while driving
  • Bad smells entering the cabin
  • Poor performance from the HVAC system
  • Noisier than usual AC or heater functions

How often to change the engine air filter

As air filter technology evolved, so has the service interval for replacing them. Mechanics used to recommend changing the air filter whenever you changed your oil. That’s no longer the case.

Recommendations for how often to change the cabin air filter vary. Chevrolet says every 45,000 miles for its vehicles. Ford recommends a 15,000-30,000-mile interval. Hyundai also says every 30,000 miles but recommends every 15,000 miles for vehicles in rough service, such as driving on gravel roads and construction sites or other situations where the filter might be exposed to excessive dust and debris.

Signs you need to change the engine air filter

When your engine air filter gets clogged, it strangles the engine’s performance. Think about trying to breathe with a damp towel over your mouth while exercising. It’s not unlike what happens to your engine with a dirty filter. Here are some signs the air filter needs to be changed:

  • A drop in fuel efficiency (although this isn’t always the case because the fuel delivery system can adjust itself to a less-than-optimal fuel/air ratio)
  • A drop in acceleration and throttle response
  • Black smoke from the tailpipe, indicating the engine is running rich and is starved for air
  • An illuminated check engine light, meaning the engine’s computer has stored a trouble code related to air flow and fuel delivery
  • Stumbling or stalling on acceleration
  • The filter appears dirty. If the filter isn’t fairly clean in appearance and is loaded with dust and debris, change it

Changing the air filter

As mentioned, the filter is almost always toward the front of the engine, and the housing might have clear markings. The housing lid is usually held on with plastic clips or a bail but might be secured with screws or wingnuts that are easy to remove.

Just remove the old filter by hand. If the inside of the housing is dirty with dead bugs, dust, fragments of dead leaves or other debris, you might need to clean it with a Shop-Vac.

Some filter designs are reusable, with a cotton, gauze or foam medium that can be washed and replaced. Other performance-oriented filters might use a special oil that enhances their filtration abilities—check with the instructions on the filter. In any case, replace the filter with the new (or cleaned) one, being mindful of correct fit. If you’re in doubt, use your phone to take a picture of the old filter and how it’s mounted and oriented in the filter housing before you replace it.

Replace the filter, securely put the housing lid back on and you’ll be on your way in no time.

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At Bumper, we are on a mission to bring vehicle history reports and ownership up to speed with modern times. A vehicle is one of the most expensive purchases you'll likely make, and you deserve to have access to the same tools and information the pros use to make the right decisions.

Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.