how much gas is in your tank ?
 

ok guys, this has no dout been talked about before but what kinda mileage are you getting out of your 5.8. its a 90 f-250 4x4 and im not expecting good fuel economy to say the least but my calculations im getting around 6 to 7 mpg.that sucks my 460 was doing better than that.any ideas how to squeez some more mpg out of it ? all my driving is around town and to and from work.. FFF

Sounds like something is a miss if you're getting that kind of mileage.

There are a lot of variables....not worth starting another 'whats my mpg' thread.

You should be getting at least 10-12. I would look into the possible reasons why you're fuel is being consumed so heavily. Vacuum leak, bad o2 sensor, fuel pressure problems, tune up, etc.

If you have dual fuel tanks, its very common to have the crossflow problem where one tank refills the other. If your truck seems to run fine, I'd look into that first.