To this day, super-duty pickups do not have to report fuel economy figures. I technically own a 1984 Ford F350, with a 460 cubic-inch (7.5 L) V8, that is rotting in a family member's yard in North Carolina, which (when operative) got 8-9 miles per gallon. It's about the size and length of a brand-new Honda Odyssey; the real split is between vehicles classed as commercial, and those that were not. Even today, you can buy an F250 with no EPA ratings due to the GWVR
Funny thing is a new superduty can match or exceed the highway mileage of a new 4Runner. As long as you aren’t cruising around town or catching red lights you’re not doing all that bad. ~20MPG in eco mode.