2020 Trail boss 5.3, Towing 8x12 flat nosed enclosed motorcycle trailer with 800+ pounds CVO Road Glide..280 mile round trip 90% Highway 70-78 MPH... I got 9.9 MPG... My 5.7 Liter Tundra with 7 inch BDS lift with 35x12.5x20 used to average 12.2 with basically the same towing... I’m not really worried about MPG, But this truck definitely sucks gas down... 4800+ miles since brand new with all types of driving I’m getting 15.1MPG per the truck computer...