Need info

Friend says she has a 9 year old F250 diesel. Said it was the last year before the engine was changed. All I know. She gets 10 mpg highway empty and less when pulling a 6000 lb loaded gooseneck horse trailer. That did not seem right so I thought I would ask here. Is this normal for this truck? Could there be a problem?

Sorry guys I have a Duramax and no little of the Fords.

 

i have a 97, 2WD auto and i normally get between 18-21 MPG empty going 70-85mph

 

She did say it is 4x4. I know that will cut it down some but not to 10 mpg

 

20.4 today, and raced a few people in those 500 miles

 

I get about 20 give er take a few, I'm usually run it hard. sounds like he has something wrong to me.

 

97 with mods, 4.11 axle auto trans gets 15 Highway 17 in town.

 

My first question will be what RPMs does she run? I have found that by keeping my RPMs under 2200, I can get 2-3 mpg better. When under a load, I get about 7-9. Empty, about 13.

I have a 96 F350 CC 4x4 w/ superchips for towing.

 

Has she replaced the fuel filters, air filter or used a fuel system cleaner lately?