I get 16..sometimes 17 with my 2001 5.4 Supercrew with towing package on
highway driving and I consider this to be good mileage for this type of
vehicle, I doubt you can improve it much more than that. Maybe try driving
it a little more gently and see if it helps but in my experience this
doesn't make much difference with this truck. Towing a 24 foot travel
trailer I get 10-11 on long trips , usually with A/C on and a full load of
fuel and gear, again I consider this to be pretty good and I don't expect to
improve it much.

Has anyone added anything to their 5.4 liter Supercrew to significantly change
the gas mileage? Right now, I get 15 mpg.

Thanks,

RayJ
2001 F150 Supercrew