Must by my speedo is off the difference, which makes the MPG worse yet...

 

My stock '06 CC 4x4 gets 21mpg highway on the stock tune....i am avoiding the latest flash like the plague, even my dealer confirmed mileage and throttle response is decreased with the newer flash. hth

 

i have a 05 f350 cclb srw w/3.73 grs and stock size cooper atr's @ 65psi.the only mod done soo far was a 4" turbo back exhaust. best mileage with new ficm has been 17.8 highway running cruise @ 75mph, average around town 14-15. also mileage seems to depend on what brand of fuel i fill up with. so far marathon and sunoco have brought me the best economy.