I've had my truck in and out of the shop 3 times and not sure what the problem really is anymore.

First problem, fuel gauge reading 3/4 full when tank just filled up. Dealer replaced the sending unit. Still reading the same, Dealer replaced the cluster then it started reading full again.

Problem is that since then the mileage I've been getting is about 10mpg. It is just a tick above empty (testing it this once) and I'm at 275 miles on the tank.

I've got a stock F250/04/6.0 Lariat crew cab short bed. I think it has a 29 gal tank.

I pull a 6k horse trailer on weekends and do mostly local driving during the week. The dealer did a "test" and said it is getting 14.9 city but I don't believe them as I've caught them taking short cuts previously.

This is my first diesel (not my first big vehicle) and I have a feeling I got a lemon. The warranty work done on it before I got it is unreal. They even gave the customer a $700.00 refund which equaled a months payment for the inconveniences. HE sold id Aug 06 and I bought it Nov 06. ran good during the winter until May when the fuel gauge went crazy.

Any ideas?

I'm taking it to a non dealer diesel mechanic on Tuesday...I'm sick of this truck already.

 

hmm... i know LOTS of guys (myself included) who get around 10 mpg. some of them are stock , some are lifted. the only thing that ever helped me to increase my mpg was an SCT from matt at spartan and some custom tunes.
i've not tried an economy tune, i've only tried the race files, and they gave me almost 4-5 mpg improvement. i'm sure an economy tune might help more for long trips.