Renting a 15 foot U-Haul to drive from Portland to Denver. Don't have a ton of stuff but enough that it will be moderately loaded. I will be towing my car on a trailer (I've been living car-free in Denver for a month).

Does anyone know what kind of gas mileage I can expect? Their website says 10, and Google searches on the subject of what a realistic useful payload will do to the fuel economy have turned up dry.

Trip is 1300 miles. I've budgeted so far for worst case scenario of 5mpg (50% of what they advertise) which puts my trip fuel cost around $800, and a best case scenario of 10mpg as advertised which would be around $400.

Any of you have any practical knowledge of what efficiency I can expect?