# Replacing your air filter won't improve your MPG. **URL:** \ **Category:** Shift518 Automotive\ **Created:** [August 18, 2010, 9:00pm UTC](https://forums.speedlife.net/t/replacing-your-air-filter-wont-improve-your-mpg/254035 "2010-08-18T21:00:22Z")\ **Posts on this page:** 1\ **Showing post:** 9
**Author:** ![KrazyKid](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/krazykid/32/6371_2.png) [@KrazyKid](https://forums.speedlife.net/u/KrazyKid)\ **Post date:** [August 19, 2010, 9:25am UTC](https://forums.speedlife.net/t/replacing-your-air-filter-wont-improve-your-mpg/254035/9 "2010-08-19T09:25:39Z")
> [@New project EF hatch](https://forums.speedlife.net/t/new-project-ef-hatch/32407/63): > > its all a huge marketing scam … like said before fuel is proportionate to air being entered on a car " mass air sensor " so if less air = less fuel , k-n air filters only offer marginal gains maybe 1-2 hp as a drop in unit . if a full c.a.i is used maybe more . the cool hoover sound most cars make at w.o.t with a c.a.i is actually bad as the motor is pullin in more air that can be used and making it very turbulent . take my car for instance it has a c.a.i but the motor needs more air so u will never hear it have the hoover sound . this has been known for yrs , not sayin keep the nasty air filter in there as the motor will deff run more efficiantly but not as big a deal as made out to be I am going to play devils advocate. The hoover sound is harmonics and like you said air turbulance. Example. 4.0L ford motor, has that ribbed black dick looking intake tract, straight to a GIANT round airfilter and air box. Its silent. replace it with a traight hunck of aluminum tube with the same inside dia, leave the filter and air box. hoover sound. same with a 1.8T VW. the ribbed turbo inlet pipe and ribbed baffeled airbox cuts the turbulance down and makes them silent. I put a K&N drop in, into the stock air box way back when i first got the jetta. was silent. MAF read only like 15Grams more under WOT highest boost spike. didnt do shit for performance or sound. Shaved the air box, and then added some more holes to the air box and removed the “ram air” duct. made a tiny bit more sound, Grams pers sec reading at the MAF was the same. Diverter valve was silent too when it dumped. I put a CIA on. Sounded like a hoover, DV dump sounded like a BOV. GPS on the maf only went up about 20 grams over stock. total reading was 280 something IRC. So between the shaved air box and K&N 5 grams difference DIDNT create the sick hoover sound under WOT, I think it had to do with the ribbed dick intake and air box design. back on topic :thumbup mileage dropped becasue I drove the balls off it stuntin around town showing off my WOOOT-PSHHHH. :rofl --- _[View the full topic](https://forums.speedlife.net/t/replacing-your-air-filter-wont-improve-your-mpg/254035)._