Well its been a little over a week now with my new Smarty. . Hadn't gotten much of a chance to drive very far until this past weekend. I have had it set at #9 since I got it, Big Surprise. Anyway, This past weekend, I went from Northern NH down to the coast of Maine. All 2 lane secondary roads, no interstate. Rte 302 for those familiar. Filled up at home, drove to Old Orchard Beach then went to Portland for a bit then back home. Stopped prior to home in North Conway and filled up. Went 222. 2 miles and it took 10-9 gallons. They way I do math, that comes out to 20. 38 mpg. VERY happy with that as it was still set on #9 and I was playing quite a bit passing, accelerating quick, and one WOT run for top end. I usually get about 19-20 mpg on that trip so this was right in line. So it appears that it does not hurt the mileage at all even playing around a fair amount with it. Still haven't tried the "fuel saver" program yet, just can't bring myself to take the #9 out.