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Engine Air vs. Cabin Air Filter: What’s the Difference?


Most vehicles have four types of filters: oil, transmission, fuel and air. Within the air category is the engine air filter and cabin air filter. While they are both responsible for maintaining air quality in your vehicle, they aren’t interchangeable. 

From the role they play in the overall function of your vehicle to how to know when to replace them, here’s what you need to know about engine air filters and cabin air filters.

What Does a Cabin Air Filter Do?

Pollutants can come from other areas of the vehicle or outside and cause an allergic reaction or breathing issues for the driver or passengers. The cabin air filter maintains air quality inside your car by blocking dust and other allergens from entering the cabin. This type of filter can be easy to overlook until you start to notice the signs of an old, clogged cabin air filter, such as:

  • Reduced airflow when the fan or A/C is on
  • The heating and cooling isn’t performing as well as it used to
  • Musty odors coming from the vents
  • Difficulty de-fogging windows in the winter
  • An unusual whistling sound coming from the vents


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Ideally, you’ll replace your cabin air filter at least once a year, or after 12,000 miles. If you often drive in heavily polluted areas or on dirt roads, you should change the filter more frequently. One rule of thumb is to consider replacing the filter at the beginning of spring when allergy season starts for many regions across the U.S.


Changing the Cabin Air Filter

The location of the cabin air filter depends on your vehicle. Most likely, you’ll find it in one of three places: behind the passenger-side glove box, under the hood, or behind the dash. Check your owner’s manual to confirm.  


When you find it, inspecting and replacing the cabin air filter only takes a few minutes. The mobile service experts at Firestone Direct can quickly replace your old cabin air filter right where you live or work,  whether you need it immediately or want to add it to an existing service appointment. 


What Does an Engine Air Filter Do?


The engine air filter keeps dirt, dust, and other contaminants out of the engine. Engines need air to function, so maintaining a clean engine air filter is essential for your car’s efficiency and performance. A dirty filter can even cause damage to other parts, such as the spark plugs. Signs of a dirty or clogged engine air filter can include:

  • Decreased gas mileage due to reduced oxygen flow
  • Difficulty starting the engine
  • Unusual vibrations or hiccups when the engine is starting and idling 
  • The smell of gasoline due to unburnt fuel in the exhaust system 
  • Illuminated check engine light

Your engine air filter should be replaced as often as the manufacturer recommends, generally at least annually or every 12,000 to 15,000 miles. If you drive in heavily polluted areas or on dirt roads, it’s a good idea to check the filter more often. 


Changing the Engine Air Filter


The engine air filter is usually housed inside a black plastic box that sits on top or to one side of the engine. There are a few different filters available but the right one for your vehicle depends on the make and model. Consult the manufacturer's recommendations and check your current filter if you’re unsure. 

The experts at Firestone Direct can replace your old engine air filter in just a few minutes to ensure your engine continues to operate at its maximum potential.

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Ready to schedule a mobile service appointment?

For engine air filter replacement, cabin air filter replacement, or other maintenance services, book an appointment with our mobile mechanics today.