I replaced my stock fuel tank with a 65 gallon unit. The gauge never moves off of full until you've driven 300-350 miles and get down to 34 gallons, same as stock. Then it goes down at the same rate it did with the stock tank from there on. It's never given a CEL related to the fuel tank.
It sure is nice to be able drive past the fuel stations in the Yukon selling diesel for $6.65 a gallon knowing there is $5.00 fuel 200 miles further up the road.
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2007.5 2500 QC 4x4 6.7L, 6 spd auto, 3.73 gears, Westin Brush Guard, 2" level kit, rear air suspension, 65 gal Aero fuel tank, Commander gauge set, RedsBeds toolbox/tonneau cover,Franktown, CO