I have 4 trucks with 6.0 engines. Always pulling and not a problem. I do fit overdrive but I keep it in tow haul and do well. I also have a dmax that is awesome but I think when I trade again, I will go back to gas everything. I would like to get an 8.1 but is GM making that in a truck for the 2010-2011 yr? I will be looking at an 11 or 12 model year when trading again. As far as milage - I do watch it but yet don't cuz that is not my concern - I need the truck, the power and were off. In compared to fords - I don't like ours - not enough power until you about red line the thing - and then were off. Dodge - i am not running any newer styles right now so don't know.