I'm rereading this thread since I just used a link to it in another thread (somebody wanting to travel I-40).
Hubby and I are NOT strangers to diesel trucks. Not only does he have the trucking experience, but we own TWO (yes, TWO) Ford diesel trucks. One is 12 years old and the other, 18. The newer one, a turbo, gets about 15-18 mpg. Not so good on the old one.
If anyone wants to buy an older diesel truck, we're selling it. :-) No real need for two, it just happened that way.