Car Air Filter Guide

An air filter cleans incoming air from an outside source. You’ll find them in all sorts of applications such as HVAC systems in homes and buildings. The ones in your car work in a very similar way.

Changing your air filter is one of the most crucial parts of routine maintenance, but it’s also one of the simplest car tasks. Learning about the different types of car air filters will help you pick the best one for your vehicle.

Types of Car Air Filters

There are two main types of air filters in a modern car: engine air filters and cabin air filters.

What Is an Engine Air Filter?

The engine air filter provides clean air to the engine by filtering it before it goes into the air intake. Engine air filters have been around for about as long as cars themselves. Engineers quickly realized damage could occur if large particles were allowed to be ingested into the motor.

There are a variety of car air filter types available, which we’ll discuss below. Most filters use a corrugated design that increases the total surface area for blocking debris.

Where Is an Engine Air Filter Located?

The location of the engine air filter is different for every vehicle, and you should check your owner’s manual to be sure. However, they’re often in the front right or left corner of the engine bay near the headlights.

You can follow the air intake tube back from the engine itself to find the filter’s location. It’s usually in the sealed airbox. The airbox lid can sometimes be popped right off. For other models, you’ll need to unscrew the bolts holding it in place.

If you have a carbureted engine or short ram/aftermarket intake system, it should be easier to find since it'll be a large cone or ring.

How Often Should You Change Your Engine Air Filter?

Most engine air filters need to be changed or cleaned every 15,000 miles. You should follow the recommendations in your owner’s manual for air filter changes.

How to Tell If Your Engine Air Filter Is Dirty

A dirty air filter is easy to spot. If there’s loose dirt packed between the folds or it’s dark gray or black in color, it definitely needs to be replaced. If you hold a paper filter up to a light source and can’t see light coming through, you might need to swap it out.

A slight drop in performance or efficiency might signal that your air filter is dirty. However, a dirty air filter isn’t likely to have a noticeable impact on performance. It never hurts to give it a quick glance every 5,000 miles or sooner.

Are Car Air Filters Universal?

Most car air filters are vehicle specific, however there are many options for affordable, universal filters that work on a variety of filter setups. Be sure to check the manufacturer's list of vehicle fitment for each filter you buy, to make sure it will work with your car.

What Is a Cabin Air Filter?

A cabin air filter is a type of car air filter that provides clean air to the passengers by filtering it before it’s distributed by the climate control system. It prevents dirt, dust particles, and allergens from contaminating the air inside the vehicle.

Cabin air filters became widespread in the early 2000s. Many vehicles made before then don’t have a cabin air filter.

Where Is a Cabin Air Filter Located?

The cabin air filter is typically located in the interior, usually inside or below the glovebox. You can replace these yourself, but it can be harder to access than the engine air filter.

How Often Should You Change Your Cabin Air Filter?

The cabin air filter should be changed every 20,000 miles or so. Check the owner’s manual for your service interval. A cabin air filter replacement is often performed by dealers or mechanic shops, but you can also do it yourself.

How to Tell If Your Cabin Air Filter Is Dirty

A bad smell (musty or moldy) or stale air coming from the AC system can be a symptom of a bad cabin air filter. It’s definitely worth checking your filter when this is the case. If you find it to be gray and dirty, it’s worth spending the money to change it. They’re usually pretty cheap.

Car Air Filter Materials

There are three main types of materials used for engine air filters: Paper, synthetic, and foam. Cabin air filters are almost always paper, but some are made of synthetic materials that can be cleaned and reused. Foam air filters are very rare in cars, but sometimes used in particularly harsh environments.

Paper Air Filters

Paper engine air filters are the most common kind. Virtually all cars come with paper air filters from the factory. Most drivers will replace their air filter with a paper one as well.

Car manufacturers want the engine to receive the cleanest air possible. As a result, paper filters tend to be very dense and good at filtering out small particles. However, this high air quality often comes at the expense of less airflow. This is the main reason enthusiast drivers swap their stock filters out for performance-oriented ones.

You can’t clean a paper air filter like you can a reusable synthetic one. You simply replace them every 15,000-20,000 miles. If you drive in dusty or dirty environments, shorter intervals are recommended. While paper filters are cheaper upfront, a reusable filter can save you money in the long run.

High Performance Oiled Air Filters

Reusable oiled air filters are typically made of synthetic gauze or cotton with oil sprayed on the surface of the material. This is also what gives the filter its red coloration. These types of car air filters are designed to maximize airflow, giving your engine a bit more air to burn. The open design offers more surface area for air to flow, while the oil traps any contaminants that might otherwise enter your engine.

High performance oiled air filters can give you better power and throttle response. In truth, we’re talking about very minimal gains. You won’t really see noticeable air intake benefits unless you get a complete cold air intake and an electronic tune to go with it. A much more noticeable benefit is the increased sound of air being drawn into the intake. This is especially true for engines with forced induction, like a turbocharger.

Even if you don’t care about extra performance, the ability to wash the filter and reuse it is a big reason to upgrade to a high-performance oiled filter. As long as you clean and maintain an oiled filter, they can last for up to 100,000 miles or more.

For some owners, the hassle of consistently cleaning a filter and the higher upfront cost is just not worth it. If you do decide to go with an oiled filter, keeping up with the maintenance is extremely important. Oiled filters should be cleaned around every 10,000 miles for maximum performance.

If you would like to learn how to maintain a reusable air filter, check out our performance air filter cleaning guide.

High Performance Dry Air Filters

Similar to an oiled filter, a high-performance dry filter has a more open design in comparison to a stock paper filter. This allows for a greater volume of airflow through the filter. While many dry filters use paper material, they use higher quality paper with more layers than a stock paper filter. Some use a cotton or gauze material.

High performance filters are ideal for engines that require a large volume of air for maximum performance. Engines with high horsepower, especially boosted engines, will highly benefit from upgrading the stock filter to a higher quality dry filter.

While these filters don’t need to be cleaned like an oiled filter, they will need to be replaced around every 15,000 miles.

Some of the top brands of performance air filters include K&N, AirRaid, Injen, and JLT.

Foam Air Filters

Foam engine air filters are the rarest kind for cars. They’re often used in machines that run in very dirty environments, like ATVs, tractors, dirt bikes, and cars in extreme motorsports like rally racing.

For cars, foam is more commonly used as a protective wrap over a cone filter. Foam wraps, like this K&N one, can improve your filter’s effectiveness in extremely dusty environments.

While paper and synthetic filters will draw in less air when debris is stuck on their surfaces, foam filters don't suffer from this problem as much. That's because foam filters have more air passages than surface filters do. This enables them to work well even when conditions are very dusty.

On the downside, foam filters are tough to properly clean and oil (which is required for effective use). They'll also break down over time if they're not properly maintained. Small bits of the broken-down filter can then be ingested into the engine, potentially causing damage. It’s for these reasons that foam is usually used in conjunction with other filters, rather than as the sole air filter.

Engine Air Filter Shapes

Engine air filters come in a variety of shapes. The configuration depends on many factors including the type of intake system the vehicle has and whether it’s factory or aftermarket.

Rectangular Air Filters

A rectangular (or panel) engine air filter comes standard on most vehicles. Some performance air filters are also rectangular. They fit squarely into the airbox, which is the protective case around the filter. The airbox helps prevent excess hot air from entering the engine.

Cone Air Filters

Many performance engine air filters are cone-shaped or cylindrical. Most are aftermarket, but some performance cars come with conical air filters from the factory. You can swap your stock rectangular filter out for a conical one with ease. They’ll fit nicely in the airbox with no issues if they’re approved for your car model.

A cone-shaped filter has increased surface area for air to be drawn in. Most aftermarket cold air intakes include cone filters. Remember, a filter on its own will only add minimal power gains.

Check out some examples below of universal air filters in this layout.

Circular Air Filters

Many older engines, specifically carbureted ones, use a circular or oval-shaped engine air filter. Since the carburetor (where air and fuel mix) is on top of the engine, these donut-shaped air filters sit on top of the motor.

This provides an opportunity to show off a good looking design when you have your hood popped at a car show. For that reason, many classic car enthusiasts care a lot about which air filter and air cleaner they choose.

Does It Matter Which Type of Car Air Filter You Use?

For most drivers, it doesn’t matter which type of car air filter they use. Performance drivers that are adding other mods will often switch to a performance air filter right away. It’s a very affordable component that takes a couple of minutes to install.

Even if you’re still rocking the stock air filter, you’re hardly missing out on “hidden horsepower” from your engine. You might only get a few more horsepower from a performance air filter. A cold air intake and electronic tune can offer a 10 hp or more increase. Many cold air intake kits include a performance air filter.

At the end of the day, the best air filters for your car are the ones that are clean.