A Tutorial on Air Filters: What They Do and How Often You Should Change Them

Every car needs a strong flow of incoming air to work optimally. The air filter is sometimes overlooked, but it’s a part of the engine that serves very critical purposes.

The air filter has two major functions, to clean the air entering the engine and to protect the engine from debris while operating. For every one gallon of fuel consumed by the engine, it needs 10,000 gallons of clean air to power the car. The less air the engine receives, the less efficient the engine will be and, as time goes by, it will likely need significant repairs.

When an engine receives less or dirtier air, the air will combine less with the fuel, and extra fuel will be burnt into soot or otherwise left over in the engine. Obviously, these deposits cause problems within the engine and the car's overall performance.

Symptoms That the Air Filter Should Be Changed

Reduced Gas Mileage

Cars with dirty filters demonstrate weaker performance on gas mileage. Cars need to have both clean air and fuel to perform optimally. Dirty filters serve as an obstruction to the critical air flow needed. Not only your car's performance but your wallet will feel the impact too, as more fuel will be needed to reach the same amount of mileage than before. It is estimated that drivers save between 15 to 30 cents per gallon of fuel when their cars have clean filters.

Cars with fuel-injected engines use an internal computer to manage the imbalance in gas and air, so gas mileage will be decreased but more gradually when operating with a dirty air filter. Keep in mind that a dirty air filter will still impact a car's performance in many other ways.

Difficult Starts

If an engine experiences misfires or difficult starts or has a jerky start, these are classic indications of a dirty filter. These complications occur because the extra unburnt fuel will gather as soot in the engine and gather around the spark plug. Under these sooty conditions, it is more difficult for the fouled spark plug to start.

Reduced Horsepower

If you feel jerkiness or a lack of response when you accelerate your car, this is another likely sign of an overloaded air filter. When the optimal combination of air and fuel cannot be reached inside the engine, the performance of the car will lag. It will be more difficult for the engine to adjust power and speeds when operating with a dirty air filter.

Smell of Gasoline or Visible Smoke and Flames from the Exhaust Pipe

When less air reaches the engine than needed, excess gas will be left over, and it will either accumulate in the engine or leak out of the exhaust pipe. A lack of air in the engine can produce the smell of gasoline when the car is started, and some fuel may even drip out of the exhaust pipe. Also, if black smoke or flames are visible from the exhaust pipe, then it is very likely that the air filter must be changed, and other parts of the engine should be checked. If your car is experiencing these symptoms, see a mechanic as soon as possible.

Service Engine Light Turns On Before Expected

Overall, as deposits accumulate in a car, expect to see the “Service Engine Soon” light turn on before you expected to see it. If you get an early warning like this, absolutely have the air filter checked by a mechanic. Often air filters can become clogged by pollen, dust, and other substances that will not be visible even in bright light. A qualified mechanic can determine the precise status of your air filter. If you are concerned it may be more than your air filter, take this free diagnostic online test to understand your car's status better.

In General - How Often Should Air Filters Be Changed?

Every 12 months or 12,000 miles in clean and dry environments; however, in dirty, dusty, rural, heavy traffic, or humid areas it should be checked every three months. Remember, air filters can be overloaded by particles that are invisible to the human eye. A qualified mechanic can evaluate the status of your filter and how it may be impacting your engine.

A clean filter can increase gas mileage by as much as 17% and can increase acceleration by 10% or more. You can prevent many unnecessary problems with your engine by ensuring you have a clean air filter in your engine.

The older or dirtier the air filter is, the lower its effectiveness. Checking the air filter should be a routine part of car ownership because air filters are critical for optimal performance.

Unfortunately, air filters are sometimes overlooked by mechanics. Ensure your car has a clean air filter, and you will save significant money on repairs and fuel.