I got into a debate with another blogger the other day. He is a mac guy that has a mostly mac blog, but got side-tracked on hypermilling. He was giving tips on fuel effeciency and I questioned a few of his suggestions. My comments begin where I point out that NASCAR does not run slicks because it reduces aerodynamic drag, but rather becuase they don't drive in rain, or snow. (duh). He never addressed that part, but instead kept debating his claim that aftermarket air filters save gas. I was going to put one on my truck when I got it since I am going to keep that thing forever. I was going to do it to save gas. Then I started to think about it. They claim they increase HP, and they try to get you to associate that with saving gas. But the more I thought about it I realized this: They test engines on a dyno under full throttle where the engine needs to suck in tons of air and that added flow increases HP. But under normal conditions you can get plenty of air in and so MPG is not increased. I tried to explaine that to him, and he would not give. On the last comment I added (which he never posted) I told him that a K&N for my truck is $50. A fram is what? $5. I drive in the city. I am smart enough to know I can blow the dust out with my compressor and so I change it about every few years (or whatever) That would take me a hell of a long time to get my money back. But the best part was where I linked to K&N's site and quoted them. They said "K&N makes no general fuel economy claims, however we encourage you to try our air filter for yourself. " I told him that they spent a whole page going on and on about HP improvements and how they dyno proves it. With gas at $4/gallon, don't you think they would claim it helped if they could? Instead they say that there is no proof that it does anything, but you are welcome to give us a bunch of money and try it out.
Anyhow, I thought it was a fun debate, although i think it was cheezy of him to not post my last reply when he had no response.