This last weekend I went on trip from Northern Wisconsin to Milwaukee(250 miles), all highway driving @ 75mph. Once I got into Milwaukee I did about 75 miles of city driving. I filled up the truck and averaged 18.8mpg. I returned home last night and had 300 miles on the trip when I fueled up. That tank was only 15.2mpg. I have a 2000 F-250 Crew Cab Short Box 4x4 with a 7.3. I did not have the truck loaded any different on the way home. I am wondering if it was bad fuel? Any suggestions would be helpful. Thanks

 

Easy checks are-

1. Bad fuel
2. Fuel filter, may be related to #1
3. Air cleaner
4. Brakes

Eliminate those possibilities and then go from there.

Waxy

 

could also be your oxygen sensors

 

In addition to the above suggestions: maybe winter fuel??......my mpg always drops a little with that.