I have a 99' Southwind 32V with a big Ford V10, Full Banks exhaust package and chipped. It is really nice to drive, passes other motorhomes and trucks going over mountain passes. Pulls my boat or the jeep with ease. If I keep it under 70 on cruise I regularly get 10 MPG. Towing the jeep or boat or running faster it gets 6 to 8 mpg. Not bad at all and so far no mechanical issues. I keep the oil and filters changed. Great chassis.
My last motorhome was a Dodge 390 that got as good as 8 and as low as 6 and it was only 22'. We are very happy with the V10 and we got a killer deal on it though in todays market you will likely get even a better deal on one.