They are pretty good but concern about SCA in coolant on 7.3L they prone to cavitation.
I miss my 87 F250 6.9L NONTURBO 2wd with 4 speed. Those will get me 20 mpg without try effort. But I do coast most time when toward to stop. Rev to redline I think 3,300 is max.
Only couple I hate. Oil leaks, HARDEST start in 10oF it RATTLE, LOUD on highway at 55 mph, and electric issues for alternator.
2000 F350 7.3L powerstroke auto. MPG SUCKY 16 in winter city and summer 17 / Highway it 19-21 due leak and boost leak. Expensive to fix if breakdown.