[tentcamper]

For you mileage drop, I think it all comes down to the size of you engine and your axle gearing.

The smaller your engine the greater hit you will take on the mileage drop because it has to work that much harder. My little V6 delivers about 24 mpg on the highway with the TM on a 600 mile trip it was getting about 16.5. About what I expected. With the same TV and a popup with about 60% the frontal area of the TM, it was getting about 18 MPG

But with my TV, it's my daily commuter. I like that 16 to 18K miles a year I get 24 mpg. So I will stay with the V6 when I get a new TV and take the larger mileage hit on our 4k miles per year pulling the TM.