I've had three Chevy Duramax Diesel Duallies, 2005, 2011, & 2018. The 2005 pulled two TT, a 24', then a 30', then a 35' Fifthwheel. Saw very little mileage difference between them. The 2011 pulled the 35' 5er, then a 40' 5er then a 43' 5er. Again ver...