Fact Checked

What is an Air Filter?

Katharine Swan
Katharine Swan

An air filter is an important part of a car's intake system, because it is what allows the car to "breathe." An engine needs an exact mixture of fuel and air in order to run, and all of the air enters the system first through the air filter. This catches the dirt and other foreign particles in the air, preventing them from entering the system and possibly damaging the engine.

Car air filters are generally pretty cheap, due to the filter's simple construction. Most are paper-like or fibrous material, folded accordion-style and arranged on a plastic or metal frame. Some are made out of a cotton or fabric-like material, which is then oiled in order to increase airflow. Vehicles generally have a specific holder for this filter, which is usually a plastic or metal box. Generally, the holder is connected to the intake manifold by a large plastic tube through which the air flows.

A dirty flat air filter.
A dirty flat air filter.

Having a clean air filter is important for your car's performance. This means that filters should be changed regularly, or the vehicle's gas mileage will suffer. A dirty filter can also cause other systems to run ineffectively, such as your emissions control system, which regulates the car's air-fuel mixture. It can also cause your spark plugs, which ignite the fuel in the combustion chambers, to foul, as there will be too much fuel without enough air; if your spark plugs foul, you may have problems keeping your car running.

A clean flat air filter.
A clean flat air filter.

Most people should change their air filter at least once a year, but those who live in areas with dirt roads or heavy pollution should do so more often, as these factors can cause a filter to become dirty more quickly. You can have a mechanic inspect it, and change it if necessary, during an oil change or your yearly tune-up.

If you plan to change your air filter yourself, look for a large plastic tube leading away from the top of the engine. The tube should connect to a large box that may be round or square, plastic or metal. The box will have a top that comes off to access the air filter. If the filter material is blackened, the dirt is restricting the passage of air and the filter should be replaced.

You might also Like

Discussion Comments


The air filter helps us by saving fuel in all automobiles. If the air filter is damaged then the mileage will go down to one-third of the ideal mileage.


My observations derived so far from the above contributions, came from post 9, which states that flammable liquids shouldn't be use for cleaning an air filter, because it can cause a fire. I believe that. I have witnessed it myself, so be careful.

In addition, my question is what to look for when checking the air intake filter? I think that first thing to look out for when checking the air intake filter, is the healthiness, because the healthiness determines the performance.


That is the sound from air moving through the supercharger. A K&N filter doesn't suppress noise like a paper filter, just a side effect of having more airflow. It's normal. You'll just have to live with that noise forever since the filter you put in never has to be changed again.


if you replace your air filter and forget to tighten one of the hose clamps, can you lose your whole tank of gas?


Hey guys i just installed a new podfilter instead of the stock filter into my car. I thought it would make the car sound better and increase the fuel economy but all it seems to do is make it louder and somehow less powerful? what does this mean? it feels like its lost its "guts" and doesn't have any go about it?


Dirty air filters do not change gas mileage. The modern computers in cars always keeps the mixture correct. All of your information in this regard is incorrect and should be changed.


how can you possibly find a tissue in a car air filter? it happened when i took my car to the mechanic as the car had problems, air filter was really dirty and greasy tissue found inside. Car had been serviced and filter changed only a few months ago (this is what mechanic said). Tissue was removed and problem solved. How can you explain?


If I install the air filter upside down, is that going to affect the airflow and cause the car to stutter occasionally?


Do not use any flammable substance to clean your filter. Doing so will introduce flammable vapors into the engine combustion chambers and could also result in a spark igniting a fire under the hood of your car. Only clean a filter that is cleanable and follow the recommendations of the filter manufacturer for cleaning.

No, do not run without an air filter. The air filter traps contaminants before they enter your engine keeping the systems clear of debris.


would it hurt or help a vehicle not having an air filter, when it is performing at high rpms?


Air filters are very good indeed, especially when used indoors. Most people think the air outside is more polluted than the air inside, but that's not true. The air inside is actually more polluted than the air outside. Funny, but true. Anyway, thanks for sharing this once again.

Air Filterer


my car air filter is dirty. can i use petro to wash it?


Let's not forget that the supercharger does make a whine anyway when you hit the gas. That is very typical. I have a 2002 40th Anniversary GTP and mine makes a whine when I hit the gas which is actually the supercharger pushing the air.


dude its probably vibrating where you broke it when it starting to suck in more air as you step on the gas pedal. This is because when you step on the gas it open throttle to let more air into the engine.


Hi, I am a "wannabe" do it yourselfer, and today, I purchased a new K&N air filter for my 2000 Pontiac Grand Prix GTP Supercharged. So during the installation process, I accidentally ripped that little adhesive strip that comes with it, but figured it was no biggie, after I was done installing it, I decided to take it around the block, the reap the benefits of my DIY work, only to my extreme disappointment and concern, to hear a whining noise, that sounds like a power steering problem, but it obviously wasn't that, and it only made the noise when I gave it gas. Help me! What is the matter?

Post your comments
Forgot password?
    • A dirty flat air filter.
      By: Edward Stephens
      A dirty flat air filter.
    • A clean flat air filter.
      By: withGod
      A clean flat air filter.
    • A clean conical air filter.
      By: nastia1983
      A clean conical air filter.
    • A clean cylindrical air filter.
      By: Javier Castro
      A clean cylindrical air filter.
    • Mechanics can inspect and replace air filters if they need changing.
      By: Linda J
      Mechanics can inspect and replace air filters if they need changing.