Good deal!
I'd think a popup would do a bit better on fuel. Diesel I presume by your numbers.
Our full height camper turns 18 mpg empty into about 12 with camper and 15 mpg empty to about 10-11.
Although, hook a 6-7klb boat behind it and it doesn't seem to get much worse.
70-75mph into a stiff headwind camper and boat netted me an all time low of 7-8mpg though this summer. Definately cleaned the carbon out of the engine!
Yeah and keep an eye on the fridge on propane. high speed with big head winds or crosswinds will tend to blow out my fridge once in a while. I'm in the habit of checking it now when I stop if I'm hauling butt down the freeway or hit some wind. Ours switches to DC if the flame goes out, but fridge uses a lot of DC power.
