the 5.8 did not get much better mpg than a 460 Weight of truck plus when ford first came out with fuel injection they said do'nt plan on getting great gas milage .the later 95 to 97 did get better ford used a different cam and heads on the 95 96 f150 and Broncos I;m not sure on the f250s I got a 95 f250 4x4 460 5spd stick and with all the mods I have made duel exhaust trottle body spacer and air intake the best I have ever gotten is 13.5 on the highway thats keeping it around 65 mph over that milage realy drops Just driving around I'd say about 10 mpg and it really don't make much difference how you drive it