I had a 96 2x4 auto that I just sold. It was really bad on gas when I first got it 84,000mi used, noticeably worse than my 95 4x4 manual tranny truck 246,000. A few things helped me out. Running 93 octane fuel, although $$$ showed better mileage, thereby saving me $$$ in the run. Startron additive, normally for boats is a non-corrosive fuel additive and runs well in these older high mileage trucks. New ignition coil and good cleaning of all components and connectors. Make sure you are running the exact Motorcraft spark plugs called for on the hood tag. When I replaced the crap plugs that were in there, I bought substitutes by another brand, they ran great for two months then they burned very uneven and basically self destructed. My mechanic told me to use only the exact Motorcraft called for and nothing else or I was asking for trouble, he was right. Then check all the sensors for function as listed in the repair books like Haynes, my TPS was dirty and acting bad, I cleaned it up good and was much better.
Good Luck, enjoy your truck!