Am I missing something here? ruley2 shouldn't complain about crappy fuel mileage... Because why?
Hopefully the 6.4 owners will get better mpg as their engines break-in just as a lot of other light duty diesels have in the past. It seems to be the only complaint 6.4L folks have with their trucks. Although there are some reports of excellent mpg of 18-20 mpg highway. IMO short trips kill mpg and might be increased as wider viscosity oils (5W40) properly rated for the 6.4L become available in the near future.