K&N air filter caused a huge mpg drop?

SpoiledRider · Jan 31, 2025

I just moved to California, and the closest Lincoln dealer is a bit of a drive, so I figured I'd do my own 20k mile service. I changed the oil (new Motorcraft filter), the cabin air filter, and even put in a K&N air filter. Before, my Nautilus 2.0T engine was getting a pretty consistent 22-24 mpg. But right after I swapped in the K&N, my gas mileage tanked to 19-20! I'm gonna do the math myself next time I fill up just to be sure, but is it even possible for a new air filter to make that big of a difference? Has anyone else had this happen after switching to a K&N?

MightyMax · Feb 4, 2025

I did the preventive maintenance on mine myself too! Sounds like your Nautilus might be a little too excited about that K&N filter!

It’s possible the new filter is letting in more air, which could mess with your fuel mixture and efficiency, especially if the engine’s not adjusting right. Keep an eye on those numbers. I ended up giving the stock filter a second chance, it’s not as flashy but it might keep my MPG where I want it

banda_ · Feb 5, 2025

I might just stick with the factory filter if I were you.

VeryGoodDriver · Feb 20, 2025

That's a big drop in your mileage! Even though K&N filters are meant to help your car breathe better they can sometimes hurt your fuel economy. This can happen if the filter has too much oil on it or if your car's computer can't handle the extra air. The oil can also mess up a sensor the MAF which controls how much fuel your car uses. Make sure the filter is installed properly and check for air leaks. You could also try cleaning the MAF sensor. If your mileage is still bad try putting your old air filter back in.

yoursobasic · Wednesday at 10:26 PM

SpoiledRider said:
I just moved to California, and the closest Lincoln dealer is a bit of a drive, so I figured I'd do my own 20k mile service. I changed the oil (new Motorcraft filter), the cabin air filter, and even put in a K&N air filter. Before, my Nautilus 2.0T engine was getting a pretty consistent 22-24 mpg. But right after I swapped in the K&N, my gas mileage tanked to 19-20! I'm gonna do the math myself next time I fill up just to be sure, but is it even possible for a new air filter to make that big of a difference? Has anyone else had this happen after switching to a K&N?

Any luck? Have you tried their suggestions? I am also planning to change mine and upon reading this it made me think twice.