[Davidg]

I would suggest you go back to the beginning of this thread. Check the fuel mileage on other 6.7 engines in trucks with single rear wheels. Check other Ford diesel forums. You might learn something. Comparing the 6.7 to the 6.4 is just ignorant. Plus consider driving habits. The fact that you have a tuner suggests to me that you may have a heavy right foot. I'm just an old grandpa, and I drive like one, therefore, I get great fuel mileage. Have a nice day sport.