Does A New Air Filter Improve Your Car's Performance?

Air filters play a vital role in a combustion engine's operation, and changing them is easy, although be careful, as you might make one of the many mistakes when changing the air filter. As a result, upgrading an air filter with one from the most popular air filter brands is one of the most popular modifications for drivers looking to juice maximum performance out of their car. However, just because you can make a certain modification doesn't mean you should, and there's plenty of evidence out there that shows an expensive air filter isn't necessarily going to give a car a performance boost on its own.

Several outlets have launched side-by-side comparison tests to see if performance air filters can boost a car's performance, and the results haven't been encouraging. A dyno test by Mighty Car Mods showed no discernible performance improvement in a Subaru Liberty RS between an OEM air filter and a performance filter, while a similar test of a Honda Civic Si by The Drive found only the smallest difference in power output. In the latter test, the priciest air filter actually generated the least horsepower of the bunch, although there was only a 2.1 horsepower difference between the best and worst filters. In a different comparison, YouTuber Sergiu Gabor also found that fitting a performance air filter to a Skoda Octavia didn't result in any noticeable power increase.

The above tests show that, for many cars, fitting a performance air filter isn't going to have any significant impact on power output on its own. Manufacturers generally design the car's OEM filter to ensure it isn't a limiting factor in performance, although there are always going to be some exceptions to the rule.

A comparison by Engineering Explained saw a marginal performance increase in a Subaru Crosstrek, with a performance filter increasing the car's power output by around 3%. The Crosstrek in question is a 2016 model, which makes 148 horsepower in stock form. A 3% increase would translate to around 152.5 horsepower. It's safe to assume that most drivers wouldn't be able to notice any significant performance difference on the road with only 4.5 horses to play with, but it is an increase nonetheless.

The other way an air filter might make a bigger difference is as part of a wider package of modifications. If you own a car that's easy to mod and are looking to transform it into the ultimate high-powered daily driver or track day weapon, you'll undoubtedly be looking to fit as many performance parts to your car as your both it and your wallet can accommodate. If other engine components are upgraded beyond their stock capabilities, then the air filter is much more likely to start becoming a performance bottleneck, and so upgrading it alongside those other parts can make a bigger difference.