We traded our 07 classic LBZ for a 2011 LML.same type 3500 CC DRW's. We get better milage towing and empty on our LML than we did with our LBZ including regens. I have only had 3 regens in 2200 miles. So the DEF is a plus in my book. Don't panic guy's, bottom line I'm getting 1.5 mpg towing and 3 mpg better empty on this new truck. And our LBZ only had the Cat and EGR. And this new truck blows our LBZ away with power while towing. And I thought our LBZ pulled great and it did. So go figure?