High Fuel Economy RVs?

"High fuel economy" and "RVs" somehow seem in seem incongruous in the same sentence.  Good mileage RV could even be considered an oxymoron.  Yet, as fuel prices continue to climb, manufacturers are working all the time to improve fuel economy.  Diesel was once a solution to low fuel economy and high gasoline prices.  Diesels typically got better mileage and diesel fuel used to be less expensive than gasoline.  Then, with demands for ever more sophisticated motorhomes, diesel fuel economy declined as rigs got bigger and heavier.  At the same time diesel fuel prices have skyrocketed.  The rising price of diesel fuel irritates me.  Diesel is essentially the dregs left over from refining gasoline.  An increased demand for diesel for ordinary automobiles has no doubt forced the prices up instead of down.

One way of achieving fairly good mileage with a camping vehicle is to tow a light trailer, like a tent trailer or tear drop trailer, behind a vehicle that gets good mileage.  Of course you will sacrifice many of the conveniences and comforts of  larger motorhome or travel trailer, but you will get better mileage.

There are some Sprinter chassis with Mercedes diesel engine based motorhomes today that are claiming fuel mileage in the mid-teens, something almost unheard of for motorhomes --at least since the 1970s.  Back then there was a 24' motorhome based on the air-cooled, rear-engine Chevrolet Corvair with a true monococque chassis that sported 15 MPG and could cruise at 60 mph.   It was called the Ultra-van. There were fewer than 400 of them manufactured, but it is estimated that more than 100 of them are still on the road today. They were designed by an aircraft engineer in the 1960s and built much like an aircraft fuselage, giving them fairly good aerodynamics and light weight. I suspect the aircraft aluminum construction has been a factor in their longevity. Interesting that the era that produced the biggest, gas-guzzling muscle cars also produced the most fuel efficient motorhome. I recently read the original brochure for a 1984 Fleedwood Southwind Eagle 1 27' Class A motorhome.  Their testing achieved 14.8 MPG at 55 MPH with an optional diesel engine, pretty good for a Class A motorhome! 

Aftermarket gimmicks that claim to improve fuel economy abound.  They range from magnets that attach to fuel lines to elaborate water injection systems.  So far, none of these gadgets has earned approval by any competent testing facility.  Water injection may have some actual positive effects:  it can increase octane, which may allow you to use a lesser grade of gasoline, and it helps cool the engine. The first water injection systems were intended to help clean carbon deposits from the combustion chambers, but I've never heard of that being successful either.  I don't think carbon deposited on metal at high temperatures is particularly soluble in water.  Ever tried mixing charcoal and water?  We've all heard rumors about the 200 mpg carburetors and how they've been systematically and maliciously suppressed by the oil companies.  Well, a chemical analysis of gasoline quickly proves that there simply isn't enough energy available in a gallon of gasoline to produce that kind of mileage.  As always, if something seems too good to be true, it  is probably a hoax.  That being said, there are differences in fuel systems.  Modern computer-control fuel injection tends to deliver better performance and mileage than older carbureted systems and there are some carburetors that deliver higher performance and some that do deliver better (though not spectacular) fuel economy.  If you have a carbureted engine you might be able to improve performance OR improve fuel economy by switching to a different carburetor.  But, be aware, you will typical sacrifice power and performance to gain fuel economy and vice versa.  One  upgrade that CAN deliver improvements in both is the Banks Power Pack, that improves delivery of air to the engine and reduces back pressure in the exhaust system.

"Airtabs" are teardrop shaped vortex generators that are said to improve fuel economy on large, square-backed vehicles like over-the-road trucks and RVs.  They are a little pricey, about $220 per vehicle.  A few users claim improved mileage, most report favorable improvements in handling in crosswinds and blow-by from passing trucks.  I'd be willing to bet it would take quite a while to re-coop your investment in fuel savings but the improvement in handling may provide immediate rewards that would make it worth while.

YOUR best bet to maximize your RV fuel economy is to keep your RV in good running condition (well tuned), make sure your tires are properly inflated, and drive carefully.  Avoid jack rabbit starts and quick stops.  Maintain constant speed on level ground and downshift as necessary when climbing hills.  Keep your total weight as low as you can.  Travel with empty holding tanks whenever you can. Choose level routes when you can and, if you have a choice, avoid driving in windy conditions.  Head winds are the worst when it comes to affecting fuel economy; cross winds can affect handling and lower fuel economy; tail winds might give you a little boost.  Minimize the stuff you carry on top of  your RV as they impact aerodyamics as well as adding weight.  The square shape of many RVs have the aerodynamics of a barn door.  I once read that the coefficient of friction for a certain Class A motorhome was the same as Jaguar XKE.  However, the total drag on the motorhome was, of course, much greater because of the much larger surface area.  Given the huge surface area of RVs, keeping them clean and well-waxed can help reduce wind drag and give fuel economy a slight boost.  Products like Protectall, claim to work well.  Protectall is reasonably priced and easy to use.  It was invented by a pilot to maintain minimum drag on the surface of his private plane.  I have personally tried Protectall and found it lives up to its advertising in both ease of use and performance.

Save fuel!