I had a 08 GMC Max (6.0), i bought a 22+5 inline trailer... Needless to say i sold the truck, and bought a diesel. Empty around here in Dickinson,ND, i be lucky if i got 10 mpg. Last year headed to Cooke city, (our usual riding area) we averaged 7-9 with an open 3 place trailer. So i figured i was only gonna get 6 if i was lucky loaded round trip with the enclosed. I'm hoping to get anywhere between 12-16 with the diesel, i'll keep updated as soon as the snow flys!!!!