I have, many times over. I drive to the Bay Area or Sacramento a couple of times per month to visit my girlfriend, friends and family. (It's about 200-280 miles each way, depending on where I exactly I go.) If I run the A/C I always get worse gas mileage. It's usually about 1 mpg worse with the A/C, but sometimes less. Obviously not a huge hit, but worse nonetheless.

 

You want a see a difference, try running nitrogen. I have it in my tires and have them set at 34 psi. Smooth ride and the tire wear is guaranteed to be minimal. The nitrogen doesn't allow for the pressure changes you will experience with air, especially due to temp changes. I suggest you check it out. I will post from time to time to report on the tire wear(if any).

 

yeah, but if you're into adjusting your tire pressure at the track, it might not work out...unless you bring a tank with you.. :P

 

My gas milage always goe up after I change the intake or exhause by 2+ mpg. I don't shift until I hear something that sounds like power.