'91 F150, 5.0L eats oil, 119K miles.
Just drove West of Detroit for a Camaro and had it loaded to the gills with spares. Did just fine. Keep fluids in it, you'll be fine. Unless you have a known trans problem, should be ok. Make sure you have good pad/shoe life for off ramps and it's cool.
I get about 12 when I'm towing my Jap tinker toys, I think we were close to 8 hauling American Iron.
I assume you are wondering if your truck will make a journey, not what MPG it gets? May help to know what you have/any known issues it has.