600 fuel mileage?

[BGParks]

Still say 17.5 mpg @ 70+ speed.

If my truck was getting those figures, i wouldnt let the dealer touch it. 17mpg at 80mph??? :-laf right! I would invest in a new calculator. Im sorry but there is no way those figures could be correct. my guess is you are not filling to the top of the neck on both fill ups.

First off my fill up is done the same way every time that I'm checking mpg. Fill with nozzle on fast till it shuts off then fill with nozzle on slow till it shuts off (I do the slow shut off twice). While this may not be as exact as filling till you see the fuel at the mouth of the filler neck doing it the same way every time should yeild close to the same results. Also as stated my numbers are averages of many fillups done this way which should help to rule out errors. Recently went from Dallas to Houston and back to Dallas. Almost all freeway driving. No load on vehicle (this is normal for me the only thing I pull is a boat and don't pull that on trips). AC off and cruise set on 75. Result, 17. 125mpg. Conclusion, I probably shouldn't have said 80 mph as I don't do that very often. I ususaly set my cruise at 5mph over posted limit which means I'm usually running 75mph. I still say I get 17+ mpg at 70+ mph. I'm sorry you're not getting mileage this good, but I am.

 

[WarrenSims]

i've got 2004. 5 600 single wheel 3500 quad cab 4x4 with 315 bfg tires and automatic transmission with 373 gears and edge box set on max performance and get 15 mpg on computer in traffic in jacksonville florida and 17. 5 going 65 mph on the computer and i have not hand calculated yet... ... max hp setting on the edge box gives me the best mpg

 

[joeyou]

With a 6sp, 2wd, and 3. 73 gears I've been seeing consistant mid 20's over the past several tanks. Daily commuting and driving conservatively.

There is no way you're getting MPG in the "mid 20's" (25mpg. ) Either you're reading the mileage off your trip computer or your calculations are wrong.