4 cyl. has little power, the truck weighs a lot. the gearing is poor for the engine powerband, gears are to tall, shifting puts you too low in the next gear/lugging badly. if the trans had 6 gears instead of five it may work. gas mileage at 20-21 mpg is poor for such a gutless power-plant. get the 6 cyl. and power is great and you will get 18-19 mpg.
i bought this truck thinking since it wasa 6 cylinder manual transmission id save gas but i thnk the engine isnt strong enough to pull its own weight. i was getting the same mpg with my old 2000 f15 which i had for 10 years. its my own fault for not asking for the carfax. in this day and age where gas is about to be 4$ per gallon it was a huge mistake; time to trade it in asap and buy a small car to save money on gas. the service engine light is always on first had to get the fuel indicator fixed and now its on yet again =(