Most manufacturers and professional mechanics recommend changing the engine air filter every 15,000 to 30,000 miles. A handful of manufacturers recommend longer change intervals of up to 45,000 miles, but this is the exception rather than the rule.
Filter change intervals are often dependent on driving conditions. Hard driving or regular driving under harsh weather conditions necessitates a more frequent air filter change interval.
The best way to know when you should change your engine air filter is to consult the owner’s manual since each owner’s manual will have the engine air filter change interval unique to your specific vehicle.
What is an Engine Air Filter and What Does it Do?
An engine air filter is a barrier that prevents dirt and other debris from getting into your engine and clogging it up. An internal combustion engine relies on air to run. As an engine runs, the air is sucked in through the air filter. It then enters the engine’s combustion chamber when the intake valves open and the piston draws in the air as it moves downward.
Fuel is also injected into the chamber at this point. As the piston rises up through the combustion chamber, it compresses the fuel and air that has been drawn in since the intake valve is now shut. When the fuel and air mixture are fully compressed, the spark plug fires, igniting the fuel and air mixture.
The resulting explosion pushes the piston back down, creating the movement of the engine which ultimately enables a vehicle to move. The exhaust gases are allowed out of the combustion chamber and through the exhaust system as the piston rises again and pushes them out.
Even though the air filter only seems to affect the very beginning of the cycle that ultimately makes an engine run, explaining how an engine works and how it uses air makes it clear how beneficial a clean and fully-functional air filter is.
What Factors Affect Air Filter Life?
No matter what is considered to be a normal air filter life, there are several factors that could decrease your filter’s life or necessitate that it be changed sooner than expected.
Dirt, Debris, and Pollution
Dirt, debris, and pollution are exactly what your engine air filter is designed to prevent from getting into your engine. Excessive amounts of each of these will decrease your air filter’s life.
Frequently driving on dusty roads, living in a location that is known for heavy pollution, and living in an area known for being particularly rough will clog the air filter quicker than an area that has less dust, dirt, and pollution.
Since an engine is constantly using air as it runs, the air is also constantly being filtered. The same concept applies when you dust a very dirty surface as opposed to dusting a well-used table that you dust every three days.
The duster head for the table might have to be replaced every three or four dustings, but the duster head used on the rarely-cleaned surface may only be used once before it must be changed.
Harsh Weather Conditions
Harsh weather conditions contribute to the premature breakdown of many different things. This is especially true of vehicles with various moving parts. Extremes in both heat and cold can cause just about anything to wear out quicker than normal on a vehicle, including the engine air filter.
Age is another factor that causes the breakdown of just about everything, but it is also something that cannot be avoided. As the air filter ages, it becomes less effective and dirtier, even if one lives in a relatively clean and pollution-free area. Even though age may not cause an air filter to become clogged or fail prematurely, choosing an inexpensive air filter to try and save money may not be a wise choice.
A quality air filter will usually perform as expected and may even come with a warranty. Less expensive filters may do better than expected, but cost-cutting measures may not always pay off.
A damaged air filter will also not be able to perform as expected. If damaged, an air filter, will not be able to catch debris that would otherwise get into the engine.
Many different things can damage an air filter including rocks, leaves, sticks, and even animals. Most vehicle air filters are under the hood and placed within a protective box called the airbox.
This is meant to protect the filter as much as possible while still allowing air through the filter. Some filters are more exposed without an airbox, but many of these are usually tucked away in a protected place within the engine bay.
Aftermarket air filters are often designed to increase airflow to the engine by being less restrictive. This often means being larger and eliminating the stock airbox. These filters are more likely to be damaged from outside factors or even during the process of shipping because of the relative lack of protection compared to the stock air filter.
Water is an engine’s worst enemy. Water that gets through an air filter has the potential to totally destroy an engine. Similar to how an air filter is positioned to avoid damage, it is also positioned to remain out of the water. Many modified off-road vehicles even position the air filter above the roof to avoid the possibility of water penetrating the filter.
What are the Signs of a Clogged or Defective Engine Air Filter?
There are generally two ways in which engine air filters can fail. The first way is when they become clogged and prevent air from entering an engine.
The second way is when they are defective or worn out to the point at which they allow too much air – and other materials – past its protection and into the engine.
There are several ways that your vehicle can show the signs of an engine air filter obstruction or failure.
Decreased performance is the result of a clogged air filter not allowing enough air into an engine. For an engine to run properly, it needs the correct amount of air. This is particularly true under hard acceleration or aggressive driving.
Though this is not usually the type of driving conducted under normal circumstances, a clogged air filter can also have an effect on the engine when not being driven hard. This type of effect is similar to running when you are out of shape and gasping for air.
Decreased Fuel Efficiency
Similar to a decrease in engine performance, fuel-efficiency is at its best when a vehicle can easily take in the air it needs. When airflow is prohibited, the engine must work harder to get what it needs. The result is a decrease in fuel economy. This usually goes hand-in-hand with decreased performance.
Check Engine Light
There are a large number of events that can make a vehicle’s check engine light come on. Vehicles today have a huge number of sensors and computers that regulate how they run.
When a sensor becomes clogged or damaged or when a sensor tries too hard to compensate for a problem, it can trip the check engine light. It is not too common for a check engine light to come on solely from a clogged or damaged air filter, but it is possible, and the filter problem usually causes several more issues as well.
This can be caused both by prohibiting airflow or allowing too much airflow to an engine.
A misfire is when one or more of the spark plugs is not properly able to ignite the fuel and air mixture within one or more combustion chambers. Many things can cause this, but the two most common causes are clogged spark plugs or a fuel delivery issue.
Defective or damaged air filters that allow too much air, and with it, too much dirt, can easily foul a spark plug and cause an engine misfire. Like the check engine light, a misfire is rarely solely caused by a damaged air filter, but it can be one of the contributing factors.
This can have long-term effects on the engine, including eventual engine failure, if not addressed.
Dirty exhaust is the result of dirt or debris getting through the engine filter, burned up through the combustion process, and sent out the exhaust of the vehicle.
A misfire is usually the end result as continual dirt buildup will usually foul the spark plugs, but dirty exhaust can happen easily with very fine particles that get through.
Again, this is usually the result of too much getting through the filter, signaling potential damage, and the necessity to find a replacement.
Under normal conditions, most experts and manufacturers recommend changing the engine air filter every 15,000 to 30,000 miles. A few vehicles have longer recommended change intervals, but each vehicle’s owner’s manual will outline the change interval for your particular vehicle.
Several factors like extreme weather, excessive dirt, and filter damage can necessitate an earlier-than-expected filter change. Signs of an excessively clogged or damaged filter include decreased engine performance, engine misfiring, dirty exhaust, and decreased fuel-efficiency.