I hand calculated mine (avg several weeks each) before and after installing my programer and saw a 2 MPG increase after installed. It was hard ( to control urges ) but kept the same driving habits before and after. I avg 10-11 towing and 16-17 daily driving. I knew how much my wife was planning on spending for xmas in 2010 so that was my xmas present, the money was gonna get spent anyways so figured to get something usefull. I believe changing the converter lock points also helps in MPG gain.
2011 Jayco Jay Flight Swift 264BH
2008 XLT SCab 5.4L, FF, 4X4, 3.55 LS, Gotts Mod w/Drop in K&N, Holley Hooker Aerochamber Muffler, Edge Evolution, Tekonsha P-3 Trailer Brake Controller,33.5" Nitto Terra Grapplers.