well she has a 90 f-150 with the 302 and a 5spd and its 4x4 and she gets about 6mpg and that can not be right cause one of our friends has a 90s f-350 with the 460 and its auto and crew cab long box sittin on 35s and she gets about 10mpg and my girlfriends truck is stock so theres gotta be somethin wrong that makin her get that bad of gas mileage, so do any of you guys know what it could be? thanks

 

a lead foot?

 

Damn dad's 92 F150 and 81 150 both get around 15-17 MPG.

 

It's a '90 , probably worn out .
How many miles on it ?
Ever been rebuilt ?
Tired rings , injectors worn/plugged open , sloppy bearings.

 

Calculating correctly

 

A full tune up would be a good place to start.
Plugs, cap, rotor, wires, fuel fitler, air filter, and O2's. If its anything built in the 90's and haven't had this done it needs it.

 

Are the brakes dragging at all? Its just an idea...

Check for a fuel tank leak, my father had a 1992 F150 and it developed a fuel leak in one of the two fuel tanks. He did not notice, I was the one to just catch it out of the corner of my eye one day. Check over the fuel tanks espcially the edges. There was a leak about 5/8 up the tank... causing him to achieve what he thought was really bad MPG... but it was becuase he wasnt even getting to burn it!