My '02 4x43500 dually never got above 16 and that was only 1 or 2 times. Mostly it averaged 15.5mpg. I never towed really heavy but when i did tow I did not notice much drop in mileage. I towed an 7.5'x20' flatbed twin axle with 3 motorcycles and gear from MD to SD and I averaged 13-14MPG on that trip running flat out 80-90MPH. (Edge Juice on level 1)truckbabe;1579866; said:Brand new 07 3500 Duramax Dually and I'm only getting 9 mpg. My 99 Ford 7.3 powerstroke dually got 17. What's up with that?
Did you change the tire size? Are you running #1 or #2 fuel right now? Do you have the high idle set, that consumes a lot of fuel. It was -20 here last weekend and with all the idleing with a few short hops we did, I went through 15 gallons of fuel. Don't trust the DIC, always hand calculate the mileage. It's winter in most areas and diesels for the most part don't like the cold. If you have the winter grille cover put it on. That will decrease the amount of time it takes to get the engine up to optimum temp. Also, the transmission is just starting to learn how you drive. Put some miles on that baby and it will get better. I noticed that after I started doing some serious towing the mileage empty got better.truckbabe;1579866; said:Brand new 07 3500 Duramax Dually and I'm only getting 9 mpg. My 99 Ford 7.3 powerstroke dually got 17. What's up with that?