When I was an apprentice mechanic, running to the parts store and getting back to the shop with the “right parts” was like winning the lottery. Thankfully, it is almost foolproof today.
Car air filters are not universal; they are model specific. However, some makers may share power plants so that service parts will be identical.
In this post, I’ll share how to order your filter. How to fit your air filter and why a good filter is so important to your car’s health.
Air filters come in many different shapes, sizes, and porosity. The right filter for your car is extremely important; an ill-fitting filter will allow unfiltered air to enter the engine, which could badly damage your engine.
It’s not uncommon for different car manufacturers to collaborate on engine development. The same engine is often found in different makes and many models across the range. Service parts for these cars are usually interchangeable.
What Is An Air Filter And Why Is It Important?
Car engines use fuel and air proportionally; the more fuel you burn, the more air your engine sucks in. But before the air gets to mix with the fuel, it first passes through an air filter.
Most cars use paper filters; the material is arranged in a pleated formation, increasing airflow by increasing the surface area.
Although we call them paper filters, it’s not paper as we know it; it’s a resin-treated paper mixed with synthetic fibers.
Air filtering removes 90% plus airborne contaminants.
Every car has an air filter which has two main functions:
- Filter the air
- Settle the air
Air is extremely important to all vehicles, and that’s because the air around us contains Silica dust and other debris.
Silica dust is basically rock partials, which, if not for your air filter, would sandblast your engine intake system and cause premature internal engine wear.
You’ll find Silica dust in soil, roads, concrete, and the levels of silica increase anywhere these materials are worked. Manufacturing, fabrication, construction, etc.
A car air filter looks unimpressive and unassuming. But it’s responsible for keeping abrasive dust as small as 5 microns from destroying your motor. As a reference, human hair is about 50 microns, so when you think about it, your air filter is a pretty advanced kit.
If not for the air filter, your car engine would gulp air like a hairy lab in the long run. Air entering your car engine needs to be uniform and settled. The large pleated air filter helps even out the air distribution entering the intake system.
A sensor known as MAF (Mass Air Flow) positioned inside the intake air ducting measures airflow volume before it enters the engine. This info is relayed to the ECM (Engine Control Module), PCM.
Airflow volume is mission-critical information, and accuracy is key.
More evenly distributed air makes for better airflow readings resulting in a more predictable, responsive engine.
Modern cars, as you know, are run by computers that are precisely designed and programmed around tested tolerances.
While running your car without an air filter is possible, you may even notice a small increase in power. However, in the longer term, dirt on the MAF may cause failure and symptoms such as:
- Turbocharger failure
- Engine lights on
- Trouble codes for MAF sensor faults
- Erratic idling
- Poor gas mileage
- Increased tailpipe emissions
How To Order A Car Air Filter
It’s Saturday morning. You’ve got a window of one hour to get the job done. You’ve got your air filter and tools and done your homework.
Pulling the filter was easier than you thought, but wait….that filter doesn’t look right…..Arghhh!!!!
I was that soldier, and it drives me crazy; it doesn’t happen too often anymore because we now order parts by VIN (Vehicle Identification Number).
All good auto part stores are computerized; the shop assistant enters your VIN, your car is identified, and you confirm your make and model; that’s it!
You’ll find your VIN in various locations on your car, you can google your model, but the more common places they like to hide them include:
- Inside the door shut
- Under the hood, either side to the engine bay
- Under the hood on the shut panel
- On the windshield base
- In the trunk
I take a pic of the VIN plate with my phone and bring it to the parts shop.
Can You Clean The Air Filter?
Yes, you can clean the filter, but it’s not a substitute for replacing it. Knocking the pare filter elements against a hard surface will remove large loose debris if you have compressed air that will help remove finer particles.
Use a dust mask if you’re attempting this, don’t want this crap in your lungs.
Don’t be tempted to wash or oil these filters; that will render them useless, and your vehicle will likely not run or run poorly.
How Often Should You Change The Air Filter?
Under normal conditions, the air filter should be changed every 15,000 miles. But if you live in a dusty environment, you’ll need to inspect it more often, about every five thousand.
In dusty conditions, expect to replace the filter every 10,000 miles.
If your engine is turbocharged, you’ll need to take special care with air filters; any dirt sucked into the compressor wheel can be catastrophic.
How Do I Check My Car Air Filter?
Checking your car’s air filter is easy; most cars’ airboxes will be easy to identify and access. Some manufacturers will even fit a toolless air box, making checking and replacing the filter easy.
The airbox contains the air filter; it’s likely fitted to one or the other side of the engine bay. It’s likely a black plastic rectangle-shaped box with large pipework attached. The air filter box opens in half to reveal the air filter.
Most filters are made of pleated paper; they must not be oiled or washed.
Replacing is really simple, follow these steps.
Identify the air filter housing.
Remove the airbox lid fasteners; the downstream ductwork can usually remain in place. In some cases, you may need to unplug the MAF sensor connector.
Remove the air filter and clean the air box base.
Inspect the air filter by holding it to strong light; if you can’t see the light through the pleated paper illuminate, it’s time to change it out.
If your filter passes the light test. Go ahead and tap it on the ground to remove grit. If you have compressed air, blow the filter from upstream to downstream.
Foam and performance filters such as K&N may be washed and oiled, but check with the filter maker first; generally, a special sticky air filter oil is recommended.
Fit the filter in reverse order, remembering to refit any ducting or sensor connectors.
Caution: Be sure not to leave any tools or fasteners inside the air box; they could get sucked into the engine when started, causing engine failure.
Does Changing The Air Filter Improve Performance?
A blocked air filter will cause the engine to choke, the car will feel sluggish and may idle erratically, and possibly set some fault codes in the ECM.
An unrestricted air system is important for all engines, especially turbocharged power plants.
Turbocharged engines are becoming more common as manufacturers are under increasing pressure to achieve more power from smaller, more efficient engines.
As you may know, Turbos work by using spent exhaust gasses to power a compressor wheel, pushing a larger volume of air into the engine, thereby producing more power.
However, compressor vanes turn at over 200’000 rpm, and while strong, any abrasive grit that makes it past the air filter can destroy it.
A new turbocharger can run into 1000s of dollars, and an air filter is twenty dollars.
What about upgrading to a performance filter like a K&N? Sure, a performance air filter can improve power; however, it is worth noting proper air filtering is important, and making modifications to your car could void your manufacturer’s warranty.
Many performance filters are oiled, which helps catch debris while increasing airflow. Some air filter oil will be ingested by the engine and can contaminate the MAF sensor.
You already know that the MAF is critical to your engine performance; any contamination can lead to poor running, fuel efficiency, higher emissions, and sensor failure.
That said, many cars run just fine with performance filters fitted; just follow the manufacturer’s maintenance schedule.
How much does an air filter cost? A car engine air filter usually costs about twenty dollars, but a performance car air filter may cost more about $80.
- About the Author
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.