Fuel economy was pretty much last on the list when I bought mine. The biggest selling point for the Benz was driving it and what it was like to be in the cab. Coming up on 30K with no regrets. For a 25 foot RV we have bags of room inside with the slide out and the cab seats spun around. We have spent an entire weekend inside during storms and have been quite comfortable and not felt cramped. In nice weather we spend almost all our time outside. I don't know where you're getting your 17 MPG number but 15 is more reasonable for a V6 Sprinter class C at 60-65.