Review on K&N Engine Air Filter 33-2154: High Performance, Washable Replacement Filter for 1996-2008 Subaru (Impreza, Forester, Legacy, Outback, and more) by Mark Williams

I threw this into a used 2002 Impreza with 130k on the clock. Initially I got about 20-21mpg with 87 and sometimes 87+91. - no ethanol blend. I'm now averaging 24+mpg on a regular 87 (with ethanol) and on the high 25 about 26mpg on an 87 without ethanol. I wish I could prove it, but since it's on the internet, rest assured. MUST be true :) Ethanol-free gas really helps (especially on older cars!) I didn't believe it either until I tried it. The air filter pays off. By the end of the year, this purchase could really be a bargain for me since Benjamin Franklin saved a few cents. In terms of SOUND or PERFORMANCE, I can confirm that the car felt and felt a little bit of power. and responsiveness. I also removed 1 section of the inlet which enlarged the inlet from a 2-3" square hole to a round hole over 3" diameter. The combination of these two changes made the engine more audible when the accelerator pedal was pressed. It doesn't sound like a race car, but it doesn't sound like an old man gasping for air either. The idle is also a bit more audible, and you can now hear a faint rumble. I would rate a 1-2 WHP win if lucky. This was done on a normal car. 5 Star Summary: - Delivered quickly - Fits right (your GUI works!) - Gave me more mpg - Engine sounds and runs better - Didn't break the bank