We Have a 500hp ISL (Cummins) we tare out with to many clothes, too much food, then the necessary water 115 gallons ,36 gallons of propane and 200 gallons of diesel at a hefty 41680, we have a 29' trailer that is all aluminum weighing in at 2640lbs empty, then with a 5k lb Highlander in it, and extra fuel, a second Generator, Mountian Bike, and misc items, total tare weight loaded in the trailer is 7820, total rig assy 49500. We are 8k under our Max limit.
That said at 66mph we get 7.441 and at 64 we get 7.587
Running the 12.5KW genny as well we get 6.8
Running no genny and aqua hot full bore to keep it warm in the coach while traveling, we get 6.134
and a whopping 5.5 at 75mph running the genny and Aqua hot, and no car in the trailer.
we always budget our trips at 5.8mpg, so we can use and haul what we please when we please.
We keep her loaded, and keep more than required superior maintenance on her. I don't know who loves her more Blue Beacon or Cummins. Well us of course..
Neil and Stefanie..
And as far as temps, I am an old Air Cooled guy, so they are watched closely, and we have never had our tranny over 177 degrees, and the engine over 184, purrrrrs...