When do you know it’s time to change your car air filter? A car air filter will undoubtedly become dirty over time due to its fundamental role. A clogged filter can lead to poor gas mileage, hinder engine performance, and expose your HVAC system to contaminants.
Keep reading for some common signs indicating a dirty air filter that needs replacing, how much a replacement costs, and if you can clean the filter instead.
What does an engine air filter do?
An air filter prevents dirt, debris, and road bugs from getting into your engine while allowing enough air to get into the engine’s combustion chamber.
If an air filter gets too clogged, it gets stuck and is not doing its job, leading to decreased performance and potentially causing engine damage.
Car experts typically recommend replacing your filters every 12,000 miles or 12 months, but check your owner’s manual for the recommended air filter replacement for your vehicle.
One of the best and easiest upgrades you can do for your vehicle is a reusable air filter like a K&N filter.
You’ll spend more up front, but you’ll own it for as long as you have that vehicle, because when it gets dirty, all you have to do is clean and re-oil it. You might even gain a bit of power from it, especially if it’s part of a cold air intake system.
Signs of a Clogged Air Filter
As previously highlighted, an air filter that is dirty or clogged can have a considerable negative impact on your car’s engine performance. But what are the symptoms of a clogged air filter? Here are eight classic symptoms of a dirty air filter:
#1. Unusual Sounds from Engine.
When your vehicle is idling, you should hear the classic hum of a properly functioning engine that you are used to.
If your engine air filter is clogged, it is not allowing adequate airflow to reach the combustion chamber, and you may hear popping, sputtering, or coughing noises.
If the filter screen becomes overloaded with buildup, you might hear a slight whistling sound if the airflow is limited by the thickness of the blockage, which should not be confused with a “whoosh” sound when you accelerate naturally. That situation is the engine simply sucking outside air through the filter.
In addition to the strange sounds, the vehicle may also shake or vibrate due to restrictive airflow, throwing off the air-fuel ratio.
#2. Lack of Power.
With limited airflow into the engine, your engine cannot run efficiently. If you experience poor acceleration, it’s a classic sign of a clogged air filter.
If your car seems slower, the first thing that you should check is the air filter (when diagnosing ANY automotive issue, always check for the cheapest and easiest possible cause first).
#3. Check Engine Light.
There are service lights that indicate that the air filter is bad. Your car produces some carbon deposits as a result of engine combustion.
If the air filter is clogged, it restricts the airflow into the engine. This then limits the amount of air into the engine, which means too much fuel is being burned. The excess fuel causes ample carbon deposits, which will bring on the check engine light.
To verify, you will need to scan the vehicle with a diagnostic tool since a check engine light can mean hundreds of different things.
#4. Dark and Dirty Air Filter Visually.
An air filter in a clean state is usually white or off white. In the case of a K&N air filter, it will be more plum in color.
The degree of outside dirt and debris deposits on the filter surface will define how dark it is. You can inspect the air filter manually to determine if it needs replacement.
It is often the case that all you would need to do is release a couple of clips on the air filter canister or air filter cover to inspect it. If you are still not sure if you need to change it or not, take it out and look at it in the daytime or with a flashlight to see how clogged it is.
The inner layers of filter paper inside the air filter may not have visible debris or dust and debris, even in sunlight.
Nonetheless, it’s a good idea to have your mechanic inspect the air filter when your car is in for service, and it’s important to follow the manufacturer’s recommendations regarding the air filter replacement. Most service departments in dealerships will automatically check the filter for you.
#5. Decreased Fuel Economy.
A car engine creates power using gasoline and air. With less air coming into the engine, the car engine uses more fuel (this is called “running rich“, resulting in less fuel economy.
That’s why a decrease in your MPG is typically an indication that it is time to change your air filter.
#6. Engine Misfiring.
A dirty filter will restrict air supply into your car’s engine, and some of the fuel will not burn because there is no air to combust with. This fuel generates soot residue that builds on the spark plug tip.
Thus, the spark plug cannot provide the proper spark needed to ignite the air-fuel mixture, and consequently, your car engine misfires or won’t start at all, causing your car to jerk excessively while idling and especially when accelerating.
#7. Dark smoke, soot, or flames from the exhaust.
As noted earlier, whether the air supply is restricted, it can cause incomplete fuel burning within the combustion chamber.
The unburnt fuel exits through the exhaust, hence the dark grey or black smoke.
In exceptional circumstances, you could even see flames coming out of the tailpipe. These flames are the remaining unburnt fuel that ignites from the exhaust system heat.
#8. Gasoline Smell When Starting.
If you have a really dirty air filter, another sign is a gasoline smell when starting.
With insufficient air supply, the unburned fuel is exiting the engine and may not produce sooty smoke or flames exiting the exhaust, but generates a distinct gasoline smell. This is typical of a bad air filter.
Engine Air Filter Replacement Cost
Depending on the type of vehicle you own and if you choose to have your engine air filter replaced professionally or do it yourself, the process can vary in cost.
Changing the air filter on your car is one of the simplest, most straightforward DIY tasks, which means that 95% of people will be able to put in an air filter.
The average cost for a standard paper air filter from an auto parts store is between $10 and $25. You may pay a couple of dollars less if you purchase a paper filter from Walmart or Amazon. If you are replacing a reusable air filter, on average, you will spend between $45 and $80, depending on the type of vehicle.
In addition to the new reusable K&N air filter, you will also need to buy a cleaning kit for the filter after the first year of use. Thankfully, the cleaning kit is not expensive and will last for several cleanings on your vehicle.
If you want someone else to replace the filter for you, be prepared to pay about $20-$30 for labor on top of the cost of the filter, which will also have a markup from what you would pay for the part yourself.
In the end, you will be able to rebuild the costs of the parts and labor to roughly $50-$90, depending on your car and the labor process/shops’ policies.
While some mechanics and dealerships do not allow you to purchase parts on your own, many do allow you to purchase your parts independently of them and then take them in for labor. If you want to save a little money, this could allow you to do so without getting your hands dirty.
Can You Clean an Air Filter or Not?
Whether or not you can or want to clean an air filter all depends on the type of air filter you’re using in your car.
There are three types of air filters.
- Disposable air filter
- Reusable air filter (gauze)
- Foam air filter (this is rare)
You cannot clean a disposable air filter, and the only option is to replace the part. You can clean a reusable air filter and a foam air filter, but there are specific applications that can be used to clean them, and they must be dry before installing.
Putting a wet air filter back into the engine of your vehicle will push moisture back into the engine.
What Happens to Your Car if You Run It Without an Air Filter?
Running your car without an air filter allows dirt, leaves, debris, bugs, and an array of air contaminants to enter the vehicle.
These contaminants will cause a tremendous amount of damage to the internal components of your car’s engine, specifically the pistons, valves, and cylinders. Furthermore, your engine will consume a drastic amount of fuel and oil, which can lead to catastrophic engine failure.
Ultimately, for your engine to safely and optimally perform, you will need to address the symptoms of a dirty air filter as soon as you notice it and replace the air filter in your vehicle when necessary.