We have a 2007, 33ft. Itasca Suncruiser V-10 and tow a 2010 Wrangler Rubicon. It would seem strange but there is no difference in MPG towing or not. I always drive at a constant speed, between 55 & 65.
2007 Itasca Suncruiser 33V
2009 Ford Flex Ltd. AWD Fa. Toad
2010 Jeep Rubicon offroad Toad