DirtWhiskey
Western Dirt Rat
That's not accurate at all. I see 17-18 in town and 19-21 on the highway hand calculated and corrected speedo in my 3500 CTD on 37's. Most of the Fuelly numbers for diesel trucks are from those posting while towing/loaded.
Are you putting cocaine in your tank? My 2012 5500 flatbed got 12-13 mixed, 14 max and 12 at the worst. Always, every day for 330k miles. Loaded to the hilt or empty. I'm sure the super deep gears and hard work weren't great for MPG. I guess I just work my trucks hard.