Sam I got almost 21 mpg the way home from Carlisle doing 75 mph, very little stop and go. It seems I can get better mileage at higher speeds than doing 55. Around town I ave 14 to 15 mpg. When I'm towing the landscape trailer with a load, around 8--10 mpg.

How much does the truck sit and idle? That will kill your ave.

From all in the 6.0 forum, Ford has the best air filter for the 6.0. I don't know since I still have the stock air filter.

When was the last time a Ford dealer flashed your computer? It its never been done, then have it done. There were some updates that helped with fuel economy.

I had a reflash right before Carlisle ATN's and it made a big difference.