Re: 1996 F250 460 crazy fuel milage
460ci engine = lucky to see double digit mileage.
You can try disconnecting the battery for an hour so the systems can 'relearn' everything and hope you'll gain better mileage. I get 11mpg city with my 5.9L V8 Durango, but I didn't buy it for mileage; it's for towing and hitting the trails.
Most newer V6 and small V8 half-ton trucks are lucky to average 15-18mpg. I'm lucky to average 14mpg in my Durango (with 75%+ highway miles). If I drive at 60mph I can reach 16mpg, but only if rolling hills are used to my benefit.
Best thing you can do to decrease some friction and heat, and perhaps (perhaps!) gain some mileage is to use full synthetic fluids in the engine, transmission, pumpkins, and transfer case. If anything you can drive a lot farther on synthetics, which alone is worth the added cost and downtime over standard petroleum based fluids.
Other things is extra weight in the truck that's unnecessary, tire pressures, brake caliper sticking (increases drag), and so on.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!