Save fuel

Discussion in 'RV Tips & Tricks' started by Icky, Jul 26, 2004.

  1. Icky

    Icky New Member

    Ever wonder which is the best way to save on fuel costs? There are three approaches: 1.Reduce gross vehicle weight 2.Improve aerodynamics 3.Slow down.
    Reducing weight has no appreciable effect on mpg once you reach cruise speed because weight only affects energy requirements on hills and when changing velocity (inertia changes), usually a minor part of any trip. Aerodynamics can only be changed (by owners) with wind deflectors and ground effects packages and the result is nil., approx. 0.2 mpg or so. Manufacturers could improve aerodynamic design, but at a significant increase in rv length. Slowing down has a huge effect on mpg. This is because wind load goes up as the cube of velocity. It is because to move forward, you have to lift a column of air (5 miles thick), or push it sideways to get through. At low velocities air is easy to push sideways (a linear function), however at high velocity the equation becomes non-linear due to the mechanics of compressibility of gases. At high velocity, you have to lift the column, because you cannot effictively push it around you. Try opening your door at 70 mph. Multiply 14.7 pounds per square inch by the area of your vehicle's hood and windshield (in sq. in.) You are lifting tons of air per mile and the more miles per hour = more tons per hour. It gets nasty fast. Going from 55 mph to 75 mph is approx. a 36% increase in velocity, however it is a 250% increase in wind load. This can result in a decline of approx. 40-50% in mpg in most vehicles. I tested this on several class A's and found that at 55 mpg versus 75 mpg, the mileage average changed from 10-11 mpg down to 5-6 mpg. The effect is about one third on diesels due to their torque/hp curve. Slowing down also has a significant effect on tire and brake life, not to mention drivetrain wear. Safety goes without saying. The downside however is that it takes a little longer to get somewhere (not a problem if you're retired or fired). Also a lot of people get mad if you are poking along. I just turn up the radio. Just an interesting observation by a old worn out engineer. Hope this helps someone.
  2. Gruffy

    Gruffy New Member

    Save fuel

    ;) I pull over and let 'em pass.....

    :shy: I also slow down on passing lanes and not try to "race".
  3. Suljer

    Suljer New Member

    Save fuel

    Teflon® is one of the slickest substances known. It's ultra smooth surface reduces air friction (drag) by as much as 40%. RV owners will see noticeable increases in cruising speed while decreasing fuel consumption.

    Using a product like International Yachtline Polish With Teflon (500 Ml for about $15, P/N: YMA636/500, website: will achieve the ultimate in beauty and protection for your vehicle. A brilliant deep Teflon® Shield that actually rust-proofs, weather-proofs, seals and protects your RV's finish. It's the newest product available and one that I'll be keeping a large supply of for the once every 2 year coating on my RV.

    Teflon® is in a family of amorphous fluoropolymers. These materials are similar to other amorphous polymers in optical clarity and mechanical properties, including strength. These materials are comparable to other fluoropolymers in their performance over a wide range of temperatures, in having excellent chemical resistance and in having outstanding electrical properties.

    Teflon® is an extraordinary and versatile technology. Teflon® has a coefficient of friction lower than ice, making it the most slippery material in existence. Its non-wetting properties have seen it used extensively in water-repellent fabrics such as Gore-tex and in coatings for easy cleaning surfaces. And its excellent heat resistance has meant it has been used extensively by NASA in the design of heat shields and space suits.
  4. Icky

    Icky New Member

    Save fuel

    Teflon or any other coating will have a negligible effect on aerodynamics at any highway speed. You still must lift tons of atmosphere per mile regardless of how slick the vehicle surface is. Without a change in frontal coefficient of drag, only a reduction in velocity will reduce wind drag. Everyone is entitled to their own opinion, but not to their own physics. Be suspicious of any miracle solutions that come in a bottle. The last time I washed and waxed my rv, it didn't chang the mpg at all.
  5. Gruffy

    Gruffy New Member

    Save fuel

    ;) Right on...

    :laugh: I'll throw another one at you. The end caps of the 5er are nice and round and about as slippery as can be expected. The square corners are under the overhang on either side of the truck. Mud and road splatter builds up on these corners so they are deffinitely in the slip stream.

    It strikes me this is where some sort of add on streamlineing might work....say a Gurney flap???

    ARCHER Senior Member

    Save fuel

    Hey all,
    I use a TEFLON wax and it is great. I use the same one I used on my cabin cruiser boat. Teflon does help a lot.
  7. doitright

    doitright New Member

    Save fuel

    i guess if the teflon polish works,,we can wipe it on our frypans?
  8. RRitenour

    RRitenour New Member

    Save fuel

    Tips for Improving Performance and Reduced Fuel Consumption (MPG) and Costs for RV's

    The overall objectives here are to reduce drag and friction and maximize performance of your power plant and drive line.

    First, start with techniques and items that are inexpensive but effective.

    Set a goal of how much improved MPG you realistically want to achieve and how much you are willing to spend to get there. There is a cost saving cutoff on the more expensive items that may save gas.

    Keep a record of the MPG performance before and after each series or changes made.

    The inexpensive but effective techniques are:


    The jury on high octane gas is still out. Low octane is cheaper, but may affect the life of your valves. I recently talked with a RV’er who had 150,000 miles on their RV, burned the cheapest gas they could find and still were getting good performance from their Chevy 454. I do the same and have not noticed significant difference except for the mountain states where I run high octane. You’ll pay $15-$20 more for high octane for each tank full.

    Keep tires at the correct pressure. Manufacturers specify the pressure for the loads you are carrying. Know your weight distribution to each tire. Check the pressure daily on trips, monthly when in storage and only when tires are cool.

    If you are in the market for new tires, several major manufacturers now offer a tire specially designed for RV's which is supposed to improve ride, stability and MPG.

    Wheel bearings must be properly lubed and torqued to spec to reduce drag. They should be checked at least once a year or to manufacturer’s recommendations.

    Drum brakes should be properly adjusted to reduce drag.

    Make sure the front end is properly aligned. If not, tires wear quicker and also have resistance against the forward motion of the RV, thus less MPG.

    Good shocks, Bilsteins or Koni’s will keep the tires on the road better providing more traction, control and a better ride.

    Place a bug screen in front of your radiator. By keeping bugs out the radiator fins remain unrestricted and engine runs cooler, the clutch fan stays off longer result: improved performance. Also, draining and backflushing cooling system annually will help the RV run cooler thus less clutch fan engagement time thus improved performance.


    Drive at a maximum speed of 55 MPH or as posted, if less. This is probably one of the best ways to improve MPG. Try driving at 65 MPH for one tank full and then at 55 MPH under similar road and load conditions. You'll see a significant improvement in MPG.

    Day VS Night Driving: To the extent that nights are cooler and less windy, consider traveling then. Cooler, less wind means less AC needed and less resistance due to winds thus improved MPG.

    When on the road look 5-6 vehicles ahead for slower or stopped vehicles or 1/2 block ahead to the next stop light. Start slowing immediately, enough to keep the unit rolling nice and steady. If stopped, start your roll very gradually, don’t floor it.

    Don't tailgate. This is dangerous in any vehicle and also a real gas consumer. It wears out brakes, tires, and your patience and uses much more gas. If you must stop or slow down, resume your cruising speed gradually. Re-engage your cruise control AFTER you have resumed top cruising speed. A cruise control engaged too early will try to get the unit back up to speed too fast, decreasing MPG.

    Some drivers constantly push and release the gas pedal after reaching cruising speed. Keeping steady pressure, pressing very gradually will improve MPG right away.

    Constant lane changing will force you to apply more gas and/or brakes to adjust to the speed of the new lane. Staying in one lane allows for more constant speed, thus improving MPG.

    Avoid resting your foot on your brake pedal or clutch pedal when driving. Both habits increase wear on parts and decrease MPG.

    Drive with all large windows closed to reduce drag.

    Air conditioning. Run your generator and the overhead coach AC instead of dash air. This keeps the load off the engine, allows it to run cooler and probably overall you will use less gas. Close off all unoccupied parts of the coach with a ceiling to floor curtain.

    Using cruise control: be careful here because a cruise control on a RV is efficient only on flat, near flat or down sloping roads. If you are approaching a hill keep the momentum of speed up by overriding the cruise, applying the gas manually before reaching the hill. This will help prevent the unit from lugging down. Manually shift into second gear at about 45 MPH instead of pushing the gas pedal to the floor. You'll improve MPG, your transmission, your engine and your exhaust manifolds.

    Water Load: Leaving on a trip with the water tanks full adds a significant amount of unnecessary weight. Fill only the amount of water needed to get to your destination. Then fill the water tanks, if necessary. Drain down before resuming on the trip. Less weight, improved MPG.

    Gas load. Run full only if on an extended trip unless in very cold weather. Fill up if the prices at the next stop are significantly higher. On short trips use up as much of the old gas as possible before refilling. This will keep fuel fresher and improve performance. Fill up at or near the final site if you're going to use the generator a lot. Less weight, improved MPG.

    Personal items: Take only items necessary for the trip. Less weight, improved MPG.

    Now for the POWER PLANT gas savers:

    Make sure the RV is running at peak efficiency, tuned up (dyno is best). All ignition components, plug wires, plugs, rotor, cap, coil wire should be in peak operating condition. All vacuum lines should be attached and free of cracks. Plug wires are a chronic cause for poor performance due to the extreme heat they encounter. If your wires are cracked, brittle or over 5 years old replace with premium quality wires only, cost about $40.00. Heat insulation for the wires is available.

    Gas Lines: Cracked gas or vacuum lines can cause backfiring and even stop a RV in its tracks. Change all vacuum and rubber gas lines if there are any signs of cracking or a minimum of every 5 years. Use only lines that specify "Fuel Lines" on the hose for fuel and those marked "Emission or Vacuum" for that purpose. A cracked line will not necessarily show leaking but can draw air. This is one of the most overlooked and difficult to analyze problems (along with spark plug wires) on a RV.

    Clutch fan: Make sure your clutch fan is not locked when the motor is cold. If it is locked it will reduce fuel efficiency. If it is not engaging at all the unit will overheat. If defective, replace with a factory OEM only, especially on 454's.

    Smog Equipment: Should be kept in good operating order and NOT disconnected.

    Window and Vent Coverings: Cover all except windshield and front side windows with heat deflecting tinting or cover them with foil or card stock. Close all unused vents when traveling and make sure they are well insulated. You can purchase an insulating pad that fits the vents. All this improves cooling capacity and improves MPG.

    Under the motorhome: On front mount engines completely insulate under the engine cover, called the doghouse. Kits are now on the market or if you wish, buy the insulating material in bulk from a RV repair facility. This will make a tremendous difference in heat transfer and noise reduction.

    Miscellaneous: Most RV's have numerous little holes and air leaks particularly in the front. Identify and seal all holes and cracks, silicone sealer or rubberized undercoating works well for this.

    Synthetic Oil: The claims are in favor of improved gas mileage but I don't know if the extra cost of synthetic oil gives you a cost offset on gas savings. AMSOIL claims not only improved MPG benefits but greater engine protection and life. Check the manufacturer’s recommendation before putting any additives or synthetics in a generator.

    Air Ram: If your unit is carbureated and doesn't have an air ram system into the carb, one can be devised. Make an air scoop by cutting the small end off a 12" funnel. Insert the cut funnel into a 3" or 4" flexible air intake hose and bond it. Attach the scoop to the inside of the grill. Run the 3” or 4” hose upward to prevent rain influx, into the neck of the air cleaner. The unit now takes in much cooler air and it is being forced rather than sucked into the carb, somewhat similar to a supercharger. Make sure the rest of the air cleaner is sealed to capture all the air being forced in. Total cost about $20. Get ready for improved performance.

    AIR Filter: Changing to a less restrictive air filter, i.e. K&N will result in a pay back. They claim less airflow resistance with improved air cleaning. Guaranteed for 1,000,000 miles, Do a before and after test on MPG. Costs about $35.00.

    Attaching a Magnet on oil filter will capture metal filings, reducing wear, improving life and performance of engine. Available at any hardware store, costs $2-$3 for a strong one.

    Outside Resistance Reduction:

    Air Dams: Rear Air Dams are available for Class C motorhomes, A roof air dam in the rear offers reduced drag and a cleaner rear end. I don't know why the class A manufacturers don't offer them.

    Ever notice most semi's have a rounded front and air dams on them? Why? For improved MPG. I think someone should offer air dams for RV's, as I believe they would help improve mileage by reducing drag.

    Now for the more expensive add-on items:
    The Banks Performance add-on system claims more HP but I’m not sure about about MPG gain. I would look at installing free flow headers (stainless if you can afford them) and exhaust 1st. OEM exhaust systems usually restrict outflow thus performance.

    Headers: Custom, high quality, low resistance headers and exhaust systems may improve mileage, for sure an improved power curve. Cost about $500. Unless you need added power, I would question if you will see a positive return in your investment. Depends on how long you plan to keep your unit and the number of miles you will be driving times gas mileage improvement minus cost of headers.

    Add on gear to transmission: Principal is to add gears between the stock gear ranges to keep Rpm's up and improve power curve in climbing. Also can provide an overdrive gear range for cruising range thus same runrate (MPH) with less engine Rpm's. Major vendor is Gear Vendors, El Cajon, Calif. Costs somewhere in $2-$3K range depending on your unit. They have a website.

    Fuel Savings:
    Join a super discount chain i.e. Costco, will usually have lower prices than major suppliers.

    Fill up now if you anticipate prices are going to continue to rise.

    Fill up in early morning or late evening, cooler and less crowded.

    Check internet for best prices in your area,

    Limit your camping to local areas.

    Plan long trips to states with cheaper gas.

    Drive less, reallocate your gas allowance by carpooling or public transportation to work, then apply the saving to fun in the RV.

    I hope this information helps you achieve improved performance and MPG and to be able to enjoy you RV even in these times of high gas prices.

    Just remember, if you’re getting 7MPG now as many do and you can get your unit up to 8 MPG average, that represents a 14% or 32 cents per gallon savings @ $2.25/gal.

    I welcome your comments/suggestions.

    Happy RV'ing!

    Best Regards,
    Russ Ritenour

    Additional Resources:
  9. Larry

    Larry New Member

    Save fuel


    What a nice compilation of information. It should be very helpful for those who are trying to get the best out of their RVs.

    I do disagree with some of your info though. The jury is IN on octane. Octane is a rating that defines a fuel's ability to resist pre-ignition. An engine's needs for octane are dictated by the engine design therefore the manufacturer specifies the minimum octane to be used. Elevation reduces any given engine's (not supercharged) need for octane by about 1 point/2000 ft. So, if an engine needs 87 octane at sea level, it will need 84 octane in Colorado Springs to have the same resistance to pre-ignition. Consequently, unleaded regular is 85 octane in the Rocky Mountain states where the elevation is above 5000'. So you can save fuel money by buying lower octane fuel when at higher elevations. Note, some auto manufacturers talk about the affects of elevation and temperature on octane requirements and some don't. It may not be mentioned in your owners manual.

    The fuel usage of my motorhome does not seem affected by the use of dash air at all. I just can't seem to measure the difference. On the other hand, my generator uses ~.6 gal/hr. If I normally get 6 MPG when traveling 60 MPH I would use 10 gallon/hr. With the generator and roof air on my fuel usage would increase to 10.6 gal/hr. This represents an affective decrease in fuel economy of ~6%. My apparent economy would decrease from 6 MPG to 5.4 MPG. In my case it appears that I get better fuel usage if I run the dash air vs the roof air. Of course, the roof air does a much better job of keeping me cool. :)

    In cold climates one should keep the tank as full as possible. Condensation/frost forms on the exposed inside walls of the fuel tank. This condensation/frost then becomes water in the fuel. A full tank has less exposed wall therefore less water in the fuel. This is a big problem for tow vehicles that are used for daily use. Of course, your RV should be stored with the tank full and a fuel preservative added to keep the fuel fresh.

    Just my opinion of course.

  10. gardnermtn

    gardnermtn New Member

    Save fuel

    to Icky Thanks for your explanation of better mileage. I knew this all the time with my limited knowledge of physics, but your text had it all there. Here is another example-we tow our HiLo with a Durango that is rated at (dealer) 14 MPG however on the road(not mountains) we repatedly get 15.3 MPG from driving astutely. GWG
  11. minerz

    minerz Member

    RE: Save fuel

  12. TomAndJanie

    TomAndJanie New Member

    RE: Save fuel

    Where did you get that setup? It sounds like the ideal "wing" for 5er pullers.

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