Yes! Your Car Has Two Different Air Filters

Issue 16 • Engine & Transmission Tip

If you’re now asking yourself: “My car has air filters?” You’re in the right place.

Probably one of the most overlooked protective consumable items your car relies on the engine and cabin air filters. When you get your inspection any good shop, or even your oil-change place, will tell you it’s time to replace them and offer to do so at a premium price. This is something you can most certainly do yourself. And with a reminder in your phone’s calendar and one of Fraser’s sneaky tips, you can save yourself money.

First, let’s talk about air filters in general.

Most modern cars have two. One filters the air for your engine, and the other filters air coming into your interior, often referred to by professionals as the “cabin”.

These are two different types of filters with two distinctly different purposes.

The engine air filter removes particulate matter that could damage engine parts. When the engine air filter gets clogged, performance drops. And when it gets really bad, well, your car can seem like it’s going to die. Oddly the only indicator that it’s time to change your engine air filter is your calendar… and your inspection shop. Your calendar is a lot cheaper.

The cabin air filter also stops tiny particles from fouling your air conditioning system but is just as efficient at filtering out nearby smells and other offensive odors. It too becomes less effective when clogged, but it is barely noticeable to the occupants of the car. We know many people who never even knew they had a cabin air filter because they are so well hidden. On some vehicles, they are accessed in the engine compartment, on others in the back of the glove compartment, and even under the dash, luckily almost always on the passenger’s side.

There are several types of materials air filters are made of, starting with affordable paper filters, cleanable gauze or cotton filters, and protective foam filters. These are pretty straightforward and all are comparable in their composition.

Replacing these filters follows the rule of thumb that more often is better than less often. So we recommend it at least two times a year. If you’re in the U.S., the best time to change your air filters is just before Spring and Fall allergy seasons begin. Both the engine and cabin filters will clog faster during those seasons, so if you’re up for the four times a year, then replace them again right after the onslaught of Mother Nature’s allergens subside.

Selection based on price is really a crap shoot when you come to this category of car parts. They are all basically the same, even though some manufacturers will claim better this or better that. If you’re smart, you’re going to replace them every three months, so buy cheap, and buy in bulk.

There is one exception though. Everyone knows car parts are not cheap, so here’s a sneaky DIY hack that can save you money on the cabin air filter. We DO NOT recommend you do this for your engine air filter! You have to be a little crafty, so read on:

Once you know what cabin air filter model your car needs, find one with a plastic or rubber frame, and preferably a grid or grate across one side. (See the example photo on the left.) Install, and enjoy for however long you want. When it’s time to replace it, buy the highest-quality, and largest Filtrete (or similar) hypoallergenic, super-duper air filter for a home HVAC system you can find. (See the example photo on the right). Plain and simple, you’re going to measure and cut the HVAC filter to fit the frame of your recently removed cabin air filter and replace the filter material yourself.

I personally get eight cabin replacement filters from one HVAC filter. And, I actually love changing them because I know I’m saving a ton of money doing it. And, honestly, my whole family’s allergies are just a little less intense in the car now.