gmc 2500 6.0 eng

I would trade in my 6.0 for an 8.1 in a heartbeat! But they are no longer made. I get 9+ mpg when towing 7500 lbs. same as my old Suburban. I get 15 mpg or so on the highway when not towing but I rarely drive under those conditions. It remains to be seen how long the transmission lasts. It always seems to be straining and downshifts even when going up a little slope.