Mikes_BLK_GT

Iver heard of valet tunes but not economy tunes. If you want economy then put the stock tune back on or do as others have said and load the 87tune(you can run higher octane with a lower octane tune just not the other way around), over all though I can tell you from experience its not gonig to really gain youmuch either way IMO. Sure I spend a little more(about 22cents per gallon)on 92 octane but the gas milage for mewas essentially the same.It was gears that cost me about 1 mpg but I wouldnt change those for anything and I gained most of my milage back when addding CoP's.

Nuke

You're going to spend how much to retune in hopes of saving maybe 1-2 MPG? If there WERE some way to save more than that I think word would be out. Improving gas mileage on the Stang to make any outlay worthwhile is still a mystery. Save the money for the econobox.