Monday, September 25, 2023


RVs that use the least fuel – Part 3: Yesterday and tomorrow

Before you continue, be sure to read parts one and two of this series if you haven’t already. 

We’ve looked at motorhomes that sip fuel and also travel trailer options to maximize your economy. Today, I thought we’d go back and forward in time to see what choices we have. 

It seems odd that, since fuel has been relatively cheap, we’ve gotten ever-bigger RVs with less and less consideration for fuel economy. This is true no matter what category we’re looking at—inexpensive fuel has resulted in inefficient vehicles.

This is sort of like the smoker who isn’t currently being treated for cancer lighting up again because, well, things seem okay for now. No matter how you look at it, fuel is not an unlimited resource. 

Back in Time

When fuel was at one of its lowest prices relative to our own earning power, there were still a few RV companies that tried to actually make a fuel-sipping motorhome. There are a lot of lessons we can learn from these in today’s designs, actually. 

The Corvair-powered Ultra Van was a breakthrough example of design and engineering that started as the project of an aerospace engineer and grew to a very collectible vintage RV. These are still popular collectible vehicles with a large percentage of them still in service despite limited original sales. Parts are relatively available and they even get car-like fuel mileage.

Ultra Van

My absolute favorite gas sipper is the Ultra Van, a motorhome that was created by David Peterson, who was an aircraft engineer. He took his love of fishing and desire to have a rig that could have all the amenities inside and created the Ultra Van. 

These motorhomes were successfully powered by the Corvair engine, which was in regular production at the time. That small, six-cylinder, air-cooled engine could hustle the Ultra Van along just fine. Yet the Ultra Van offered full stand-up interior height, a bathroom, kitchen, bedroom, and all the amenities of a then-modern motorhome. 

The way this works is by using aircraft engineering to create what’s known as a space frame—so the body is actually the structure. This is how your 747 is built, essentially. 

The resulting vehicle was only about 3,000 pounds. The engine at the rear meant the floor was relatively close to the ground, so that meant less height, too. The bulgy shape of these also cut through the wind pretty effectively, and you got a pretty slick motorhome. 

With today’s structural adhesives this would totally be possible to build once again. You could shove a Subaru engine under the bed in the back and it would do pretty well hustling this thing around. 


The revolutionary 1986 Vixen Motorhome may point to the future of motorhomes and represented advanced thinking.

That was actually the idea of the Vixen, sort of. But it was powered by a BMW-sourced diesel engine and got a claimed 30 miles per gallon. These came around when fuel prices were higher, in the 1980s. They were innovative and efficient. 

The idea was to build something very efficient that could also fit into a garage. There is a pretty active community that still exists around the Vixen. 

However, these had a pop-top and some other features that made them less popular with the public. Like Ultra Van, eventually the company went out of business. 

Honorable mention

There are two other motorhomes that weren’t bad with a gallon of fuel. One of those also came out of the 1960s—the Clark Cortez. The initial models were also space frame designs. But these featured front wheel drive, like most of today’s passenger cars. However, they were heavy, being built by a fork lift company. So, the economy was the result of the Chrysler-sourced 225 Slant Six—and you know this wasn’t a speed demon. Still, mileage wasn’t bad. 

The opposite end of the scale might be the GMC Motorhome of the 1970s. Yeah, it was powered by a giant Oldsmobile 455 V8. But it was relatively light for its size, and surprisingly slippery through the wind. Current owners are still bragging about fuel milage that isn’t horrible. But that 455 also is no slouch in acceleration. 

These, too, used essentially a space frame and were front wheel drive. So all the space in the back was used for accommodating the campers. There is a strong following of these today, and their build quality means there are quite a few rolling around. 

The Future

Where do we go from here? If you believe all the pundits, we’re headed down to Electric Avenue. I know lots and lots of traditionalists are going to fire up their keyboards and talk about the power grid, lithium mining and all sorts of other things that detractors of electric vehicles trot out. 

But railroad locomotives have used electric traction motors since the days when steam disappeared. It’s how you get power to those motors that can matter. 

Thor Electric Motorhome

I think one of the most promising concepts that I’ve seen is Thor’s electric motorhome concept. The reason I like this concept is that Thor sees the reality of the world. Their current idea is to use a propane fuel cell to provide power to a lithium battery system that, in turn, provides power to the drive motors. 

When Hymer came to the U.S., before everything went to heck, they had been working with a company called Watt Imperium on using that operation’s propane fuel cells. Propane, as you know, is wherever we RVers are. 

This seems like the ideal current solution as you have your all-electric power for shorter trips, about 125 miles, and then you can use those propane fuel cells for longer journeys. 

KOA recently released a study indicating that most campers stay within 75 miles or so of their homes when they go camping. So, honestly, you could use this and never tap into that propane, if this is you. If you drive 500 miles in a day, you have the propane as a backup. 

Park it without the tow rig. Credit: Thor

Trailer power

Under their Airstream brand, Thor also showed off the Airstream eStream. This concept makes a lot of sense as it uses on-board electric drive motors to overcome the efficiency losses of towing a trailer. 

What really struck me about this concept is that Airstream took the things off the roof that cause wind resistance, like the air conditioner, and moved them into the trailer. That left the entire roof for a large number of solar panels. 

As you can read in my detail on this rig, this wasn’t totally Airstream’s idea but came from Germany. 

However, Lippert did have the idea and showed a concept chassis that offers similar features to what is under the eStream. I’m still working on a detailed story on that, but the chassis offers some nifty technology. 

While all these electric trailer systems are still a look into the future, they would help our present-day tow vehicles run far longer on a gallon of whatever we fuel them with. Or, if you are towing with an electric tow vehicle, this would completely eliminate the range drain that is part of towing. 

More power to ya’

There have been a few concepts that we’ve seen, some much closer to reality than others. 

For example, SylvanSport showed off their electric concept that will use a chassis provided by Zeuss, a company that’s already making electric commercial truck chassis. 

Winnebago, too, shared the actual working concept of their all-electric motorhome, which has been on the road being tested. 

In summary 

To me, the most logical thing a company could do today is the first thing I mentioned in this article: Build something powered by a Subaru engine that uses aircraft build technology to make a lighter motorhome that has almost no disadvantages. For close to a decade, Ultra Van did nearly the same thing—so it’s not a new concept at all. Then, when an electric powertrain becomes viable that would be able to work within this concept, you could switch to that. Or offer some form of hybrid, like the concept Thor motorhome. 

Even if fuel prices drop to levels that they did pre-pandemic, I still wouldn’t complain if I found some way to get relatively good fuel economy while also enjoying this wonderful land we love to travel in. 

Of course, I guess I could always go find myself a used Ultra Van and a wrecked Subaru and be my own builder. 


I would love to read your comments and suggestions over on our new forums, where you can weigh in and start or join a discussion about all things RV. Here’s a link to my RV Reviews Forum.

Tony comes to having worked at an RV dealership and been a lifelong RV enthusiast. He also has written the syndicated Curbside column about cars. You can find his writing here and at StressLessCamping where he also has a podcast about the RV life with his wife.

These RV reviews are written based on information provided by the manufacturers along with our writer’s own research. We receive no money or other financial benefits from these reviews. They are intended only as a brief overview of the vehicle, not a comprehensive critique, which would require a thorough inspection and/or test drive.

Got an RV we need to look at? Contact us today and let us know in the form below – thank you!


Tony Barthel has been a life-long RV enthusiast and travels part-time with his wife where they also produce a podcast, write about RVs and love the RV lifestyle.


  1. Sorry to burst your bubble about railroad engines, but they run on diesel. They are in fact giant diesel generators that power electric motors. Electric motors are used because of their ability to smoothly transfer power to the wheels this greatly reduces the jolting on the coupler’s. Also the electric motors don’t bog down when applying power. Those big black things slung under a railroad engine are in fact fuel tanks that carry hundreds of gallons of diesel fuel.

  2. Hi Tony,

    What about all the recent / current class B’s that claim 22mpg or more?

    I like the economy of them but I can’t get the wife to even consider it.

  3. I have a 1956 MGA that weighs 1988# ready to drive, including 3.5 gallons of “petrol”. It was designed at a time when Shell 100-octane gas sold for 19¢ a gallon in the US, but England was still recovering from WWII. They had plenty of scrap aircraft aluminum, but needed all their steel to rebuild their bombed-out infrastructure. So, the MGA has an aluminum hood, trunk lid, and doors, and a small 1489cc four-cylinder. Yet it is as fun as anything you can drive on four wheels!

    Somtimes we really should look backwards to see our way forward. And we love Subarus in Colorado–it’s our “state car”. So, I would love a Subaru-powered Ultra Van! Maybe you could go into business building them, Tony!

  4. I have often complained about the big box A/C’s on the roof of RV’s but have seen folks who restore/rebuild RV trailers installing a split A/C on the tongue and removing the roof A/C.

    • European and some Canadian RVs have had between the frame rails, below deck a/c units built by Coleman and Dometic for years!

  5. Thank you Tony for this informative three-article series. Our current suburban weighs in at nearly 6,000 pounds! The future, not so distant, IS electric mobility for the masses. We’re also lucky to live in a province where electricity is between 5.5 and 7 cents a Kw. We’re waiting for our next puller vehicle …an electric Hummer…at 1,000 Hp, it should be able to pull our 5,000 lbs. Trailer… fun times ahead, notwithstanding…

  6. The large majority of electric naysayers that come after this comment have little to no knowledge of how electric drivetrains work.
    I have followed the tech for years but am not qualified as a writer to write further about it. Maybe it’s time for RV Travel to find someone who can bring us all up to date in a series of articles.
    Electric RVs are coming .. and fast!

    • We have planned an RV trip to Alaska this summer for about three months in our small Class C. I agree that alternative energy powered RVs are coming but how soon can be debated. When will the infrastructure to support the number of high speed charging stations needed to recharge these electric RV be available? That will require a major upgrade to the electric grid and a huge increase in the power generating capacity (a massive increase in the number of power generation stations). Both of these will take several years to accomplish if the upgrades are started immediately.

    • Don’t count your chickens before they hatch! When you see the power companies spending billions of $$ upgrading the infrastructure then you can safely say EVs are coming in mass. Until that time it’s only a pipe dream, technology has a long way to go.


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