Cut fuel costs by increasing fuel economy and efficiency.
By Peter D. duPre
Ask RVers what is the single biggest daily expense of owning a motorhome and most of them will cite the cost of fuel. As this article was going to press, the nationwide (U.S.) average price of regular gasoline was approaching $3 a gallon, and a gallon of diesel was priced similarly. In Canada at press time, prices were about 10 cents per liter higher than they were at the same time last year. The facts are (a) retail fuel prices have been trending upward for some time, and (b) fuel prices are volatile.
It seems safe to say that in the foreseeable future, gasoline and diesel fuel are going to cost more than they do today; the only question is, how much more? Dwindling oil reserves, political upheaval, stock market speculators, and a worldwide increase in the demand for oil are all putting pressure on the wholesale cost of oil. This means that the price you pay at the pump can only go up. We learned last summer that just a five-cent jump in pump prices adds $5 to the cost of filling up a motorhome with a 100-gallon fuel tank. Now in the overall scheme of things, paying an extra $5, $10, or even $20 to fill up your RV really isn’t that painful, but what happens to your ability to travel when you are on a fixed retirement income and the price of fuel jumps even higher?
I don’t know about you, but I have no intention of limiting my weekend getaways and parking my coach. My rig is a beautiful thing, but I didn’t spend $150,000 for a driveway ornament. I bought my coach to be used, and I intend to keep on using it. Sure, the rising cost of filling the tanks will have an effect on my budget, but I realized early on during last summer’s price rises that while I had no control over the price I pay at the pump, I do have control over my RV and my driving techniques.
Driving for economy
An improvement in fuel economy of 10 to 15 percent really makes a difference when you regularly drive a vehicle that gets between 8 and 10 miles per gallon. Think about it. The average gas puller gets around 7 to 8 mpg, and most diesel pushers get between 9 and 11 mpg. A 15 percent increase in overall economy means an extra 120 to 150 miles per tank, and over the course of a year, it’s like getting a free trip! What’s more, gains like this are within reach.
The simplest and most effective way to increase fuel economy is to slow down. High-speed driving costs you more. From an aerodynamic standpoint, the average motorhome is little better than a large brick with wheels. The faster this “brick” pushes through the air, the more resistance it encounters and the quicker fuel economy goes down. For RVs the magic number is 60 mph. Every 5 mph you drive over 60 mph means a 10 cent-a-gallon increase in the cost of fuel. Driving at 75 mph, for example, can mean a decrease in fuel economy by as much as 2 mpg “” more if you are bucking a head wind.
Of course, on today’s busy freeways, it is often difficult to keep your speed down to 60 mph. Traffic often moves much faster than this, especially out West. However, if you are trying to keep fuel efficiency high, it is vital that you drive more slowly “” even if it means you are still going over 60 mph. Drive in the right lane with the semi-trucks as much as possible. Long-haul drivers have to keep driving costs low. These guys usually drive at the most economical speed for traffic conditions, so stay to the right and pace yourself against the truckers. If you find you are passing more than just a few trucks an hour, back off the throttle a bit.
While on the freeway, make it a habit to use cruise control. These devices help the engine maintain a steady speed, and that means an improvement in driving efficiency, which generally equates to increased fuel economy. Cruise control works best on long, relatively flat roadways and isn’t designed for use on curvy roads, steep hills, or in town. Many drivers believe that they can maintain a steady speed with throttle pressure alone. Keeping a particular throttle pressure over a sustained period of time is very difficult, and increases/decreases in speed will occur.
Another factor that hurts fuel economy is erratic and aggressive driving. Hard acceleration from stops, braking too quickly, and other inconsistent driving techniques can easily cost you 1 to 2 mpg, as well as add wear and tear to the rig. Keep your starts, stops, and general driving techniques as smooth as possible. It will not only help increase your fuel economy, but it also will reduce overall maintenance costs and make your passengers more comfortable.
One thing that many coach owners overlook is unnecessary idling. An idling engine gets ZERO mpg, and the longer your coach idles, the more fuel it burns. Turn off the engine when you expect to be idling for more than a couple of minutes and you could see between a 2 percent and 5 percent increase in overall mpg.
One final driving tip is to turn off the factory-installed dashboard air-conditioning. If you need a little air blowing on your face, use the fan setting. An engine-mounted air-conditioning compressor robs you of both fuel economy and horsepower. Typically, these compressors draw between 1 and 2 horsepower and can cost you up to a couple of miles per gallon in economy. In addition, they can put an extra strain on a motorhome engine during hot weather, particularly when climbing hills, which could lead to overheating.
PM improves economy
Most RVers know that regularly scheduled preventive maintenance (PM) is an important key to keeping their unit running smoothly and reliably. It is also vital for achieving maximum fuel economy. Simple maintenance procedures that cost little or nothing can have a huge effect on overall fuel economy.
The number-one category under PM for improving fuel economy is tires. Improperly inflated tires not only experience irregular and rapid wear, but they can cost you in terms of a decrease of as much as 15 percent in overall fuel economy. Don’t rely on eyesight alone. Modern radials can look normal and still be 30 percent underinflated. Only a quality tire pressure gauge can give you an accurate reading. Make it a habit to check air pressure weekly, adjusting pressures as needed to the RV manufacturer’s recommendations. Check the pressure when the tires are cold or driven less than a mile (see FMC, April 2005, “Where The Rubber Meets The Road”). Also, a switch to radial tires can boost fuel mileage significantly, as much as 8 percent over bias-ply tires.
A final word on tire inflation. Anyone who has studied physics knows about roll resistance. Just to keep your vehicle rolling down the road, a certain amount of fuel is used to overcome the elemental friction that wants to keep the tire still. Less friction means less roll resistance. Fuel mileage watchers often think that by over-inflating the tires by a few pounds they can reduce friction and improve fuel economy. While this may be true, the small gain in fuel economy achieved by running the tires overinflated is more than offset by the increased wear and tear on the tires and the danger of the tires overheating and blowing out. For safety’s sake and long tire life, always stick to the vehicle manufacturer’s recommended tire inflation pressure.
Another area of tire care that affects fuel economy is wheel alignment. Keeping all the wheels in alignment helps the vehicle handle better and prevents the tires from dragging, improving fuel economy by as much as 3 percent. Check the brakes, too. A dragging brake drags down mpg.
Anytime you can improve airflow into an engine, you increase efficiency and generally reap the benefits of increased power and/or improved fuel economy. One of the best ways to do this is to replace the air filter, something most drivers don’t do often enough. The air filter keeps impurities and dirt from damaging internal engine parts, but as they do their job, they often lose efficiency, costing you up to 10 percent in fuel economy. Regular replacement of this item will help keep fuel economy high and engine wear low. I recommend buying a quality replacement such as those made by K&N (www.knfilters.com). K&N’s filter charger air filtration system has an overall efficiency rating of between 97 and 99 percent and filters out particles as small as 5.5 microns. In addition, the filter is reusable, requiring only a quick wash and oiling between when dirty.
For top power and economy, an engine needs to be operating at the peak of efficiency. Make it a point to keep your engine maintained to the factory schedule, or more often if needed. A poorly running engine can affect fuel economy by as much as 40 percent! Gasoline or diesel, make sure your engine is in tip-top running order.
The choice of motor oils can also affect fuel economy. Using the manufacturer’s recommended type and grade of motor oil can improve fuel economy by up to 2 percent, and using a thicker grade of oil than recommended can lower your mpg by 2 percent. When buying motor oil, make sure the label says “Energy Conserving” on the API performance symbol for top efficiency. You might also consider a switch to synthetic engine oil and transmission fluid. Virtually all modern engines and transmissions are compatible with synthetic oils. However, make sure you check with the vehicle manufacturer to ensure that the product you want to use is compatible with your motorhome’s engine and/or transmission. Brands such as Amsoil, Valvoline, and Castrol all offer quality products that will reduce wear and tear, improve efficiency, and give you a fuel economy gain of up to 2 percent through reduced internal friction.
MPG through housekeeping
One of the easiest ways to quickly improve fuel economy is to clean out the RV. Weight hurts fuel economy and the more your coach weighs, the more fuel it uses. Just because your unit has a 3,000-pound payload capacity doesn’t mean you have to carry the maximum payload everywhere you go. Every RVer I know, myself included, is guilty of hauling around a bunch of unnecessary stuff. Carry only what you need for a particular trip and leave the rest at home or rent a storage room.
Once the closets and storage bays are emptied, drain your fresh, gray, and black water tanks. Fresh water weighs about 8.33 pounds per gallon, so a full 100-gallon water tank weighs 830 pounds. Unless you are headed for a rough camp in the middle of the desert, there is usually no need to travel with a full fresh water tank. Most of us camp in state parks, KOA campgrounds, and other RV parks where water is plentiful. I almost never have more than 30 gallons of water on board while traveling, filling up only when I reach my destination.
Gray and black water are heavier than fresh water, because they contain chemicals, soaps, waste, and other impurities. These tanks should always be emptied after every trip, even if they aren’t completely full. (You’d be surprised to learn just how many RVers will leave 15 or 20 gallons of gray or black water in their tanks.)
Propane also carries significant weight, but because the weight of this gas varies due to temperature, exact weight is often difficult to calculate. The generally accepted weight is 4.2 pounds a gallon, so 20 gallons of propane weighs around 84 pounds.
Improved housekeeping to gain mpg also applies to the exterior of the vehicle. Just keeping your unit washed and waxed can help reduce fuel consumption. A clean and slippery vehicle offers less wind resistance, and that equates to an increase in miles per gallon. While the gains in fuel economy of a clean and waxed RV are admittedly small “” as little as 1/16th to 1/8th of a gallon per mile, it does add up. I’ll take the “free” gallon of fuel I gain every 8 or 16 miles. Besides, a clean coach just looks better.
Another area of aerodynamics that can be easily improved is to reduce the number of accessories carried on the outside of the vehicle. From a fuel economy standpoint, rowboats, bicycles, and lawn chairs are best carried at the rear of the RV or on a trailer, not on the roof. It is also a good idea to keep your towed weight to a minimum and to keep your towed vehicle or trailer as aerodynamically clean as possible.
If you’ve done all the above and are still not satisfied with your coach’s fuel economy, you can always modify the engine with bolt-on kits, rework the exhaust, or even re-power your rig. The problem with under-the-hood changes is that they don’t come cheap. Often big bucks are required for small performance and economy gains, and recouping the costs of purchase and installation can take years. So before you dash out and buy a performance improvement product for your coach, do a little research to find out the costs, the pluses and minuses, and the performance/economy gains. When you’ve done that, take a hard look at your motor coach. Most aftermarket performance products will improve power and economy, but they work best with engines that are in the front half of their life cycle. Boosting the output of a gas or diesel power plant with 200,000 miles on it may not make economical sense if the engine is showing signs of age. Instead, consider rebuilding the engine first, then adding any bolt-on equipment.
The next thing you need to ask yourself is, how long are you going to keep your current motorhome before you replace it with another? There is no point in spending $3,000 or more for a performance kit or a set of heads and headers if you plan on keeping your coach only a season or two. If that’s the case, live with the power you have and save that money for modifying the new vehicle.
Once the economic decision has been made, the time to decide what modifications to make is at hand. For that you have to decide what you want to achieve. If it is strictly economy you are after, you can get by with spending less. I always advise folks to start simple and inexpensive and work up to high-priced and complicated. So, the first thing to do is to look at inexpensive things that offer pronounced improvements in fuel economy. One of the first things to consider is ground effects, especially on older units. The undercarriage of any vehicle is just not conducive to smooth airflow; that means resistance, which cuts down on fuel economy. Consider adding a rubber or fiberglass air dam under the bumper if you don’t already have one, or repair the existing unit. A well-designed air dam will smooth out the undercarriage airflow and can contribute up to a mile a gallon in fuel economy gains (depending upon vehicle).
Although there is some controversy about its effectiveness, a relatively inexpensive fuel economy improver is to remove the clutch fan on the engine and replace it with an electric fan. The drive belt and clutch fan typically rob an engine of about 1 horsepower, and eliminating them helps both power and economy, because external drag is removed from the engine. Electrically activated fans attach directly to the radiator and offer a much more efficient way of cooling the engine. An extra advantage is that they can be switched to the instrument panel and manually as well as thermostatically activated. And because these fans will run when the engine is off, they can reduce coolant temperatures of a hot engine quickly when it is parked.
Earlier I mentioned that replacing the air filter with an aftermarket unit such as those produced by K&N Filters would improve efficiency and economy. In addition to this, consider modifying the air intake into a ram air system. These units improve and increase the flow of air into the engine, resulting in improved economy and performance.
Once the easy modifications have been performed, it is time to step up to solid performance-enhancing options such as installing a turbo kit, custom headers, a cat-back exhaust system, and perhaps a new torque converter. While often considered performance-enhancing devices, these items also can add to the fuel economy bottom line, because they improve air and exhaust flow through the engine. Turbochargers work because they have a positive boost pressure, meaning that there is more boost pressure feeding the intake side of the engine than there is exhaust pressure leaving the engine. As a result, the engine is always operating at or near peak efficiency, which improves performance and mileage. However, you may have to move up to premium-grade fuel with a turbocharger.
Custom exhaust systems work on a similar principle. By redesigning the headers and exhaust system, without affecting emissions, engineers are able to clean up the flow of exhaust exiting the engine. Although it looks like a steady stream of smoke when it exits the tailpipe, an engine’s exhaust actually comes out in “bursts.” Each time a cylinder fires, it produces a burst of exhaust that enters the exhaust system along with all the bursts from the other cylinders. Custom exhaust systems clean up the traffic jam of bursts, allowing them all to merge easily and flow smoothly out the tailpipe. The elimination of an exhaust backlog allows the engine to breathe easier, resulting in improved power and economy. Headers are also designed to increase scavenging of exhaust gases by actually “pulling” more of the gases out of the cylinders than original-equipment exhaust manifolds.
Changing or reworking the torque converter is also an option. Torque converters convert engine power into driving power in the transmission, and many of them can be improved so that they lock up more quickly and cavitate transmission fluid less, all of which saves you fuel.
A more radical way to improve economy is to consider repowering your motorhome. This is particularly appropriate if your coach is powered by a large gasoline-fueled V-8. Diesel engines are about 30 percent more fuel-efficient than the equivalent gasoline-powered engine. The things to consider here are the age of the coach and the cost of the conversion. If you plan to keep your coach, a diesel conversion may seem like a good idea, but it isn’t cheap. You can easily spend $10,000 and higher for a new diesel V-8. Plus, odds are you won’t be able to use your current transmission with the new engine, so plan on spending at least another $5,000 for a transmission and drivetrain. Still, spending $15,000 or so is a cheap expenditure compared to the cost of buying a new motorhome. Furthermore, if your aging engine is coming due for a rebuild, a complete swap may be more cost-effective in the long run.
A word of warning
A quick read of this article may give RVers the impression that if they do everything mentioned herein, they can improve fuel economy by 50 or even 100 percent. Sadly, this is not usually the case. Sure, there will always be some RV owner out there who doesn’t drive efficiently or keep his or her coach in good running order and then has an RV epiphany and doubles the unit’s fuel economy. For the rest of us, it isn’t that easy. Most of us already drive efficiently, keep our motorhomes running right, and hold our payloads to a minimum, so our gains won’t be that dramatic. However, with a little careful planning, almost all of us can experience a 10 to 15 percent gain in overall fuel economy, or between 1 to 2 miles per gallon.
Gasoline and diesel fuel costs likely will continue to climb. If so, an extra mile or two per gallon will deliver huge dividends in both money saved and distance driven.