I have an 03 2WD Extendcab shortbed. I get low 20's unloaded on highway. 17.5-18.5 in town unloaded. With my 19 foot bluewave I get 17.5 on highway. With my 36 foot 5th wheel which is a hair over 13k pounds I get 10.5 to 11.5 depending on if I can keep it at a relatively even speed. If I'm on say I-35 going down to the coast and I keep it around 70 mph I can get almost 12. If I get in the hills forget it. I've hauled all my gear with both Gas and Duramax. The diesel is the only way I will ride until they find something better. My running buddies run Ford and Dodge diesels and we all get the same mileage loaded with almost identical gear. Unloaded is where I shine. Neither of my friends can get over 19.5 mpg on the highway unloaded. My Father in law has a new crewcab Z71 Duramax 2500hd and he's getting better than 16 on the highway pulling an old champion bass boat and knowing him he's probably doing around 85-90 going down the road.

Thanks for the replies folks!
I was kickking around the idea of calling up Mr. Monte Coon, but after thinking about it I've decided to hang on to what I've got, she'll be paid for next month so I think I see what its like to not have a truck payment for a while!

I have seen 27mpg out of it. The conditions have to be just right for it to happen...if you think I'm B/Sing you, wait until it gets cold out and lets go for a ride. You have to drive it right also, very seldom does she run over 2k RPM's, shift it on the back side of the torque curve, which is around 1300-1500 RPM's, not real sure the exact rpm.... I don't stomp my foot in it in-between gears, I ease into it. Keep the tires aired to the proper inflation pressure, keep the fuel filter and air filters changed, keep the overhead ran, high flow muffler. She's light and short for that engine, being a 2wd, keeps her lower to the ground so there is less wind resistance.