Air filter
 

I've heard about some people removing the air filter and then replacing it with some kind of cloth and supposedly they get better fe. Does anyone know what the cloth is? And why does it increase your fe over an air filter? Is the cloth still ok to use instead of an air filter?

Some aftermarket filters use an oil soaked foam or cotton filter media. However, aftermarket air filters do nothing for fuel economy despite their advertisements.

If you want a low flow filter buy one, don't throw a sock (cloth) over the intake and call it good. You will run into problems with crap going into the fuel system and engine.

I think you're confusing filter vs cloth with paper filter vs cloth filter. They are both air filters specifically designed for your car, but one is disposable and one is cleanable. Don't buy a cleanable one. I'm an idiot for buying one. They don't pay themselves back for a long time (since you have to buy cleaning and oiling pack) and they sure as hell don't make your car any more powerful.

I saw an improvement with my k&n drop in filter. Yes they are expensive, but for my 03 civic it works. My escort rarely went over 2k and never over 3k so the engine never really pulled enough air for a better breating filter to be effective(65mph is at 3.5-3.6k on the civic). I also like the convenience, yes you have to clean them(eventually) but i don't drive that much so it will be a while. Do not try to make your own filter, anything that accedentally gets into the engine is a bad thing. Get one that is made for your car...and don't get a sponge one as they don't filter for very long.

air filter
 

while there is much hype about aftermarket air filters,there is no laboratory evidence to confirm advertized claims.K&N was tested against factory micronic paper element filters and found to filter less effectively,foul the soonest.Don't know about "fabric" filters.Air filters are a dead end with respect to improving mpg.They provide virtually no restriction to the intake flow,and consequently have no effect on volumetric efficiency of the engine,even at wide open throttle.There surface area is carefully computed to do exactly this.Spend your money elsewhere.

I prefer a clean engine and only use quality filters. I use Baldwin and no other brand. I am not going to get into statistics about filtering or argue on who makes the best filter because I already answered that question.

i put a k&n on my 2006 malibu and it gave me 2mpg's right out of the box

I tried a K&N on my 6000 wagon once. I did notice a bit snappier throttle response, but no better mpg. I could also buy a lot of stock paper air filters for I paid for the K&N.

Has anyone ever thought about putting a bigger box and filter into their car? Maybe there would be a bit less resistance. Just a thought