^^^^^Maybe. But surely a good "tune" that was specifically MPG oriented, would give more MPGs. I think the problem with a MPG Tune, would be the testing. You can't just put the car on a dyno, and come up with any accurate results, like a performance tune.
You've got to drive the car through several tank-fulls, under a controlled situation.....like certain temperatures, with the same type of driving. This is difficult to do, but possible.
I'll keep my guns, my freedom, and my money.....you can keep the "change".