Has anybody tried the superchip to increase gas milage?

I have heard from a ford mechanic that if you try the chip or redo the computer you have to rum premium gas , so i would probably just leave it alone unless you dont mind the extra expense

My brother has the superchips tuner on his 03 X - previous post is pretty much correct. to gain any mpg you have to run the highest tune seting and that requires you run premium.He did it for 2 tanks and got about 1.7 mpg gain.....not enough to cover the added expense of the premium fuel.