There are a few key factors to this question, the biggest of which is: what class of motorhome is being referenced in these questions? Another thing to keep in mind is that ‘green’ is an alternative, an extra luxury, not necessarily something that comes standard with the vehicle. That being said, there are a few that rise to the occasion and provide not only better gas mileage, but alternatives in design, customization, and color.
The top is a Class “C” Itasca Navion Motorhome. It can hold up to six people and it is diesel-powered. It can tow up to 5,000 pounds, and it is a favorite with conservationists who own motorhomes, since it only uses 18-20 miles per gallon.
The Itasca Reyo 25 “Q” is the biggest, in Class “A”, also diesel-powered. Despite its enormous size, the Itasca Reyo gets 18 miles to the gallon. Customer ratings are five-star, partially due to the smooth handling of the vehicle.
(It should be noted here that these two models are now under the Winnebago name. They are still available for sale).
Last but not least, the RoadTrek Adventurous RS, which is fuel-efficient while mainting a height that makes sense for the customer. With ceilings over 6 feet, there is plenty of head space.
If you’re looking for a more environment-friendly motorhome, you may want to consider one of the above options.