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Engine air filters are critical for keeping airborne particulates from damaging your engine.
Chutima Chaochaiya via Shutterstock
Gas and diesel engines still power most vehicles and look poised to be with us for some time to come, even if their dominance is waning. Any engine that develops its power from burning fuel depends on vast amounts of air for the combustion process and efficient operation.
Running under typical circumstances, your car’s engine sucks in anywhere from 150 to 400 cubic meters of air every hour. When you suck in that much air, you get abrasive particulate matter (science for "dirt") that can, over time, accelerate engine wear. Causing parts like bearings, cylinder walls, and piston rings to fail prematurely. To help stop that wear, cars are equipped with engine air filters to trap dirt and particulate matter before they get inside the engine.
Changing your air filter as scheduled is crucial to making your engine live longer and run right. Here, we clear the air (so to speak) about what engine air filters do, what they’re made of, how often they should be replaced—and how you can save a few bucks by replacing them yourself.
We looked for well-established brands that are widely distributed. We read technical papers from independent sources and reviewed detailed product information from manufacturers and end-user product reviews to make our picks. We also took into consideration our own personal experience with engine air filters we’ve installed in our own vehicles. Our Editor’s Pick was based on overall customer satisfaction, filtration performance, and our collective editorial experience.
Wix has been around for the better part of a century, and they have a long-standing reputation for quality products. You'll find them in motorsports, industrial applications, and, in some cases, our editor's cars.
The company claims its filter technology captures 45% more contaminants and lasts 30% longer than other brands. They also boast a product line of over 16,000 replacement filters, so they probably make one that fits your vehicle, no matter what it might be. Most Wix engine air filters are pleated cellulose media or synthetic non-woven fiber, depending on the application.
Price-wise, Wix is usually a little more costly than filters from Fram and other competitors, but not by much; they are a little harder to shop for on Amazon too. At this time, they don't have their own Amazon storefront, though Fram and others do. Drivers can find plenty of Wix engine air filters on Amazon; it just might take a little extra searching. Of course, traditional brick-and-mortar parts stores also carry Wix products. It's worth noting that Wix produces own-brand filters for retailers like NAPA.
Wix's warranty period is the same as your manufacturer's recommended air filter service interval.
Pros
Reputation for quality, filters available for most vehicles
Cons
There are less expensive options
No, not a man filter. A Mann Filter. Mann is a leading designer and manufacturer of air filters for motor vehicles as well as oil and other filters. Mann makes OEM-level filters and is actually the original equipment supplier for many of the big German auto brands. The company has more than 70 years of experience in filtration and auto parts design. With more than 300,000 applications, Mann is a top option to filter almost any fluid in almost any motor vehicle.
You can rely on its products for not just OE-level quality of filtration, but for the construction of the filter and fitment. Plus if the factory filter needs any extras, Mann will likely include those parts too. For some heavy-duty applications, Mann even offers optional secondary filter elements to add protection to your vehicle.
Mann may be more expensive than some brands, but their prices are normally competitive. And when you consider the level of quality in each one, the price can easily be well worth it.
Pros
OE quality, wide range of applications
Cons
Higher price, less availability for domestic brands
K&N filters differ significantly from others on the market because they use an oiled cotton gauze filter media instead of cellulose or synthetic non-woven fiber for most of their engine air filters (the company also makes foam pre-filters). K&N filters aren’t disposable either; when they become too dirty, they are washed using a special K&N filter cleaner, then re-oiled with K&N filter oil.
K&N air filters don’t meaningfully increase horsepower or torque in an otherwise stock engine. We selected them as the best filter for high-performance applications because their unique filter media is designed to maintain high airflow characteristics over significant mileage and under arduous conditions, like racing or off-road driving. Conventional air filters become increasingly restrictive and must be replaced, whereas K&N’s can be restored with a wash and oil. K&N air filters may not add horsepower, but they’ll keep the horses you’ve got running harder, longer.
K&N has been around for over 50 years, and they’re very transparent with their testing protocols and other pertinent technical information. Their filters are significantly more expensive than disposable filters, but over the life of a vehicle, that upfront cost is amortized, and you may actually spend less running a washable K&N engine air filter than disposables. K&N’s air filter warranty lasts the life of the product.
K&N also produces the AEM, Aairrade, and Spectre brands in addition to cold air intakes and universal-fit air cleaners for customizers and tuners.
Pros
Designed to last the lifetime of the vehicle, maintains high airflow characteristics under arduous conditions
Cons
May be difficult to fit in some applications, washing and re-oiling the filter takes time (but this only happens every so often)
Fram also has a long history in automotive engine filtration. Their products are offered in tiers, ranging from basic replacement level quality then graduating upwards. Their aftermarket air filter lines start with Drive, the least expensive, then move up to Extra Guard, Tough Guard, and Ultra at the top of the Fram heap.
Their Extra Guard line approaches the features of our number one pick but generally runs a few bucks cheaper when compared filter to filter. As with Wix, most of the Extra Guard filters use either pleated cellulose or non-woven synthetic fiber filter media. Fram products are widely distributed, and the company produces filters for most makes and models, so you should have no trouble finding what you need.
Fram’s packaging proclaims that Extra Guard engine air filters offer “2X” the engine protection of basic filters, but they remain coy about what that means exactly.
There’s a lot of scuttlebutt about Fram’s quality or supposed lack thereof. This editor has run Fram oil, fuel, and air filters on different vehicles over the years and never experienced a failure or any indication that the filter wasn’t doing its job. Like Wix, Fram’s warranty period is the same as your vehicle’s factory-specified air filter service interval.
Pros
Affordable, widely available, options for many makes and models
Cons
Might not be as robustly constructed as some higher-priced filters
Purolator air filters are conventionally constructed, and most use a “multi-fiber" filter media. Purolator doesn’t mention what those fibers are; we imagine they are predominantly cellulose. Regardless, their replacement air filters are claimed to have 99% efficiency; that means for every 100 grams of dust that pass through the filter, 99 grams remain trapped in the filter media. Most air filters offer at least 98% efficiency.
Purolator says their filters can improve acceleration by 11%, but we should note that replacing a severely clogged filter with a new, clean air filter of any brand will improve acceleration. Or, to put It more accurately, restore acceleration that was lost due to impeded engine airflow.
Purolator’s website has several informational videos which are potentially helpful to the DIYer, including one that outlines a typical air filter replacement job. Just like several other engine air filters here, Purolator’s warranty period is the same as the vehicle’s prescribed air filter service interval.
Pros
Meets or exceeds manufacturer's specifications, widely available
Cons
Some users had issue with fit (specific models only)
Bosch Workshop air filters are designed as moderately-priced OE replacement parts. Bosch lists over 200 different Workshop air filter part numbers, enough to provide an engine air filter for 90% of cars in the US and Canada. The customer reviews for Bosch workshop filters are high, with most scoring 80% or better.
The Workshop line employs “high-velocity” cellulose filter media and polyurethane seal, for leak-free fit and 98% filtration efficiency, according to the manufacturer. The warranty period is the same as the specific vehicle’s manufacturer-specified air filter replacement interval.
The Bosch name is as old as the automotive industry itself; the firm supplies OEM and aftermarket parts for many major manufacturers.
Pros
Affordable price
Cons
Only 98% filtration efficiency
The EcoGard name isn’t as familiar as the old standards like Wix, Fram, and Bosch, but in their comparatively short life, they have carved out a niche providing affordably-priced replacement car parts.
Most EcoGard filters use conventional cellulose or non-woven synthetic fiber filter media and provide 99% filtration efficiency. EcoGuard also offers a wide enough product line that you should have no difficulty in finding an EcoGard engine air filter to fit your vehicle. They try to get aftermarket replacement air filters for new models to market as soon as possible.
EcoGard’s corporate address is in Bridgewater, Massachusetts, and the customer service phone number and email address are listed on their website. Like the long-standing brands, EcoGard’s engine air filter warranty lasts for your vehicle’s factory-recommended filter service interval.
Pros
Affordable price, filters available for many makes and models
Cons
Not many options for older vehicles
Photo Credit: NONGASIMO via Shutterstock
Your car has an engine air filter for a fundamental reason, to protect it from being damaged by airborne particulate matter. This holds true whether you drive to the grocery store once a week or have a daily 100-mile commute.
An engine air filter is a device placed in an engine’s intake system which is designed to separate particulates from the air before it reaches the engine, where it can cause damage.
Engine air filters aren’t to be confused with cabin air filters which are part of the HVAC system; their job is to clean the air within the car's passenger compartment. Cabin air filters often look like engine air filters and use similar technology.
Photo Credit: Cherdchai charasri via Shutterstock
Various materials are used as filter media, sometimes on their own or in combination. Here are a few examples of the most common filter media materials.
Cellulose
Easily the most common filter material, cellulose is what comprises the hard exterior of plants’ cellular walls and is well-known as the material most paper is made of. Cellulose air filter media is essentially a specialized form of paper that allows air to pass through while collecting atmospheric particulate matter. Sometimes, nanofibers or other materials are used in conjunction with cellulose to improve effectiveness.
Cotton
Cotton is also used in engine air filtration, notably for performance-oriented filters like those produced by K&N. In these applications, layers of cotton gauze are sandwiched between wire screen for strength, pleated, and sprayed with a special, tacky oil that traps particulates.
Foam
Foam air filters are common on gasoline-powered lawn and garden implements and for high-performance and off-road automotive applications. They aren’t usually specified as OEM or OEM replacement.
Polyester and Other Synthetics
Synthetic fibers are also used in air filter media. Sometimes in conjunction with cellulose or on their own, often as non-woven fabric filter media. Some manufacturers have been working with so-called nanofibers, which are incredibly tiny and spun with different surface profiles to make them very efficient as filter media.
When your car’s engine runs, it draws air through its induction system; the air filter is part of that system. Air passes through the air filter, and suspended particulates adhere to the filter media through the action of separation mechanisms. A separation mechanism simply refers to how dirt “gets stuck” in the filter.
The efficiency of an air filter is expressed as a percentage which is usually determined by allowing a known quantity of test dust to pass through the filter over a given period of time, then measuring the difference. i.e., if air laced with 100 grams of dust is allowed to pass through a filter, and 99 grams become trapped while 1 gram passes through, that filter would be said to be 99% efficient. This is an oversimplification but serves to illustrate the concept.
A clean air filter vs a dirty one that needs changing. Photo Credit: Nor Gal via Shutterstock
Whatever the factory recommended air filter service interval for your engine, you should check the air filter physically a couple of times a year, or every 7,000 to 10,000 miles. If you drive in particularly arduous conditions, such as areas that are very dusty, you should check your engine air filter more frequently.
Some vehicles will display information about air filter life on the dashboard through the driver information center. Others may have a mechanical device located under the hood on the airbox, which shows airflow restriction. These usually look like a small, clear plastic canister with colored markings and a plunger that indicates the approximate efficiency of the air filter. After you replace the filter, it can be reset. Note that not all vehicles have an air filter life indicator.
Open the filter housing and remove the air filter element as described below. If the design of your air filter allows, gently spread the pleated filter media apart and check for debris. If debris is accumulating and the filter media looks very soiled, it’s probably time to replace the filter. As noted earlier, a dirty air filter might reveal itself through reduced engine performance; ideally, you will have replaced it before it gets to that point.
Engine air filters should generally be replaced every 15,000 to 30,000 miles or as recommended by your owner’s manual. Some filter manufacturers recommend doing so every 12,000 miles, but they have a vested interest in selling more filters.
Vehicles that operate in extremely dusty conditions may need their engine air filters replaced more frequently. Trucks, which are more likely to work in dusty conditions, often have a cyclonic pre-filter that doesn’t need to be replaced but may occasionally need to be cleaned. It’s integral to the air intake, and it uses airflow to remove some particulates from the air before it reaches the air filter element. These pre-filters help to extend the service life of the replaceable air filter element.
As mentioned elsewhere in this article, the primary reason cars have engine air filters is to protect internal components from the damaging effects of particulates that are suspended in the air. Particulate matter consists primarily of mineral dust, which has many sources, both natural or as the result of human activity, and much of it is silica. Silica particulates with a Mohs hardness of 7 or more are the most damaging to engine components.
If you fail to replace your engine air filter, it will continue to collect particulate matter until it can no longer pass enough air to meet the engine's requirements. At that point, performance will deteriorate, and acceleration will suffer.
What won't happen (unless you're driving a carbureted car) is a decrease in fuel economy. The reasons for this are explained in detail below.
This editor’s grandfather owned and operated an auto parts store for 50 years, and he was a stickler for fuel economy. He’d pull a fresh Fram air filter off the shelf for his truck every 15,000 miles or so because he understood that a dirty, clogged air filter would result in wasted fuel—except grandpa was wrong, sort of.
Grandpa would’ve been most familiar with old-fashioned carbureted vehicles, and with those, a clogged air filter can indeed reduce fuel economy by anywhere from 1-15%, in some cases, more; this is because the carburetor that mixes fuel and air for combustion is a mechanical device; it cannot compensate for a clogged air filter.
Thus, when the air filter is obstructed, the carburetor adds the same amount of fuel to a smaller air volume, resulting in an overly-rich mixture that won’t combust efficiently. A common telltale was partially-burned fuel exiting the tailpipe as black smoke. However, the last new cars on the U.S. market equipped with carburetors were sold over 30 years ago, and even then, they were an anachronism.
Electronic fuel injection has displaced the carburetor on essentially all gasoline-fueled passenger vehicles everywhere, and it can adjust for a restricted air filter. Electronic fuel injection measures the amount of air entering the engine both before and after the air filter; the system’s computer can use these and other data to ensure that the ratio of fuel to air is kept as close to ideal for given running conditions as possible.
If Performance is Affected, Why Isn't Fuel Economy?Let’s say your engine air filter is clogged to the point that it will only allow sufficient airflow for your engine to propel the car at 45 mph. The fuel injection will still supply the correct amount of fuel for that level of airflow, and no more. But a carburetor would simply continue dumping gas down the intake as if the air filter was new.
As a result, fuel economy remains constant with the fuel-injected car even as the air filter becomes partially clogged. This doesn’t mean you should never change your air filter; eventually, air flow would become restricted to the point that engine performance would be adversely affected. This condition will manifest itself with poor acceleration and reduced top speed.
As counterintuitive as it might be to think that an air filter clogged to the point of reducing engine performance wouldn’t affect fuel consumption, it’s true and has been demonstrated in tests performed by the Oak Ridge National Laboratory. Testing with diesel engines yielded similar conclusions.
Nevertheless, grandpa’s point of view persists in the popular imagination, largely because of experiences from the days of the carburetor.
The fact is the majority of aftermarket air filter brands design their products to meet or exceed manufacturer’s specifications for filtration efficiency.
Any of the high-quality filters we’ve mentioned in this article should provide more than acceptable protection for your engine whether you drive a Ford, a Ferrari, a Lexus, a Honda, or anything in between—provided you stick with your manufacturer’s recommended air filter replacement interval.
Even the least mechanically inclined person can renew their car’s engine air filter. If you feel comfortable swapping a vacuum cleaner bag, consider yourself sufficiently experienced to handle the job.
Before beginning, purchase a replacement air filter. You’ll need some information about your vehicle to ensure you get the correct part. Whether you buy online or at a brick-and-mortar retailer, you’ll need to know your car’s make, model year, and details about the engine; e.g., inline four-cylinder or V6 (frequently, the same model vehicle will be available with different powertrains, and they don’t necessarily use the same air filter).
If you’re not certain about those details, all cars built since 1981 have a standard, 17-digit Vehicle Identification Number (VIN), which encodes important details about the vehicle. Simply Google searching that number will yield the information you need to order the correct air filter for your car. Alternatively, many auto parts suppliers give the option of providing a VIN when ordering parts to ensure the correct fit.
You can find a vehicle’s VIN plate at the base of the windshield, on the driver’s side, under the glass; it’s also duplicated on a build sticker that’s usually located on the driver’s door or door jamb.
You should consider wearing gloves for this job because engine compartments can be dirty places and may potentially expose you to hazardous materials.
1. Spot the airbox: this is the component that houses the air filter; it’s usually boxy or cylindrical and will have large ducts leading to and/or from it. Typically, the largest ducts in the engine bay are those that carry air to the engine.
Locate your engine's airbox. Image credit: Autoguide.com.
Locate your engine's airbox. Image credit: Autoguide.com.2. Open the filter housing/airbox: this procedure differs from one vehicle to the next; many use metal spring clips and are very easy to open. Simply pop the clips off and separate the halves of the air box, revealing the air filter within. With others, it’s not so obvious. Our Fiat 500 Abarth’s airbox is held together with screws. Occasionally, you may also need to remove air ducts from the filter housing to separate it and replace the filter. It should be fairly obvious if this is the case with your vehicle. More often than not, the ducts will fasten with hose clamps. Loosen the hose clamps and gently but firmly tug and wiggle the ducts till they detach. If you really find yourself stumped here, consult your owner’s manual or take a crash course on your car at YouTube University; just apply common sense when doing so. The problem with the internet is that anyone can use it, even people who pass on bad advice.
Carefully remove the old air filter, noting its position. Image credit: Autoguide.com.
Carefully remove the old air filter, noting its position. Image credit: Autoguide.com3. Remove the filter: with the airbox separated, the filter should be easy to spot. If it’s not, make sure you’ve opened up the right part of your car! Note how the old filter fits in the airbox before removing it; this will assist you when you position the replacement. Then gently remove the filter using your hands (it’s a good idea to wear gloves when servicing vehicles).
Clean the air filter housing with a vacuum cleaner. Image credit: Autoguide.com.
Clean the air filter housing with a vacuum cleaner. Image credit: Autoguide.com.4. Clean the filter housing: visually inspect the interior of the airbox; if it appears very dirty, vacuum it out and wipe it down with a shop rag. If you’re fortunate enough to have an air compressor, you can use compressed air to blow dirt and debris out of the air box.
Insert the new filter into the housing. Image credit: Autoguide.com.
Insert the new filter into the housing. Image credit: Autoguide.com.5. Replace the filter: position the new filter in the airbox exactly as the old one. It should fit snugly, and the gasket-like rubber edge of the air filter should make even contact with the filter box.
Replace the airbox cover. Image credit: Autoguide.com.
Replace the airbox cover. Image credit: Autoguide.com.6. Replace the airbox cover: replace the airbox cover in its original position; reattach clips, fasteners, and hose clamps (if applicable). Check to make sure everything is secure before closing the hood.
January 20, 2023: Updated product links.
August 24, 2022: The article received a major update, with all how-to and informational sections being rewritten. The following products were removed: EPauto, Mann, Toyota Genuine Parts, AC Delco, and Genuine Subarus air cleaners. Wix was added as the No. 1 pick, K&N was moved to No 2, Fram Extra Guard was moved to No. 3, Purolator was moved to No. 4, Bosch Workshop was added as No. 5, and EcoGard was moved to No. 6.
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Factors to Consider When Buying a New Engine Air Filter for Your Car
Choosing the right engine air filter is more critical than you think. A high-quality filter maximizes fuel efficiency and prolongs the life of your engine. But a poor choice can lead to reduced performance and costly repairs down the line. Stick around as we'll take you through all the factors to consider when choosing an engine air filter for your car.
Filter's Size & Style
There are different types of engine air filters available in various styles and sizes. These characteristics are key factors to ensure optimal filtration. An ill-fitting filter can create spaces where unfiltered air can bypass the filter and enter the engine. Be sure to check and compare the size and fit against the previous filter to make sure you have the right size and type of filter for your engine’s housing.
Driving Conditions
If you often drive on dusty roads, your filter needs to hold more dirt. Premium filters, like FRAM Extra Guard®, work great at capturing tiny contaminants that might bypass standard filters. However, if you often drive in high-traffic areas, the filter needs are different. More cars around you mean more fumes. In situations like this, a synthetic blend filter like FRAM Ultra® Air is recommended. It offers a good balance between airflow and filtration.
Filtration Efficiency
Choose an air filter with a high filtration efficiency. Efficiency is the percentage of contaminants an air filter removes. This quality is pivotal in safeguarding your vehicle's engine. Setting a new benchmark with a 99% efficiency, FRAM Ultra® Air offers the best protection for your engine. It's an ideal pick no matter your car needs.
OEM Recommendations
Consult your car's original equipment manufacturer (OEM) specifications. These provide valuable guidance on which air filter your vehicle's engine was designed to run with. It is recommended that you choose a filter that meets or exceeds your vehicle's OEM standards.
Ease of Installation
If you take pride in doing your own car maintenance, consider filters that are designed for easy installation. FRAM offers a range of engine air filters for a hassle-free installation.
Warranty
The warranty can provide added peace of mind regarding the quality and durability of the product. FRAM offers warranties for engine air filters to be free from defects for as long as the recommended change interval. This makes your purchase less risky.
When choosing an engine air filter, have in mind your car's specific filter needs and the driving conditions. For all-around engine protection, a filter with enhanced dirt-holding capacity, such as FRAM Extra Guard® or FRAM Ultra® Air, often excels in most applications. These filters are designed for easy installation and meet OEM standards.