My Ram Cummins weighs 13,000# with a utility box that likely has as much drag as a slide in camper. (Solid, not a pop up) Cruise speed is usually 75mph. 13mpg with a light load is the best it's ever done. 15mpg empty, maybe, if I baby it. But my gas truck can do that.Are you only towing with the cummins? I have a 2500 megacab, and with winter diesel I am getting 16mpg hand calculated and in october/november, normal diesel, when I got the truck I was getting 19mpg avg hand calculated. Towing I get between 9-11, with an HQ19 Full watter tanks (about 8800lbs), and quite a bit off road in mud/dirt under 35 mph. I always drive in Tow/Haul with exhaust brake active as well which drops mileage.
This is better than my 1500 I traded, that averaged 6-9 towing and 15.5 mpg mostly highway.
It would seem, that DRW vs SRW is the same 2mpg loss/gain as gas vs diesel.
Utility box+DRW+gas engine = Just 6mpg. But nearly ALL of my city and county work trucks will be replaced with gas trucks soon. Even the F550 bucket trucks. They'll never see enough highway miles for the diesel to pay them back at all. And the diesels are less than 33% reliable per 5 years.
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