TriptekAs reported by Lug_Nut .  Last week we looked at needed dash instruments and readouts required in the operation of your RV or tow vehicle.  This week we will examine an option that may be a somewhat luxury that many already have, the fuel mileage onboard computer.  Does it work and does it provide a value?

Fuel consumption computers are found on many vehicles sold today including many RV chassis.  These display digital readouts of such things as instant MPG, current MPG since last reset, estimated remaining fuel range and more.  While all may have somewhat questionable accuracy they are still very useful.  In addition, one has to also remember that the calculations do not include consumption from the generator or any fuel burning heaters or boilers.

Unfortunately their accuracy can not be adjusted.  This is due to their method of calculation.  While gasoline and air intake are burned at a theoretical weight ratio of 14.7 to 1, it is subject to vary depending on conditions and the exact fuel properties.  Temperature for example, alters the volume to weight ratio of both fuel and air.  So repeatability is not necessarily possible.  One day’s event may well be more accurate than another. Even industrial electronic flow meters with temperature compensation are generally only accurate to a + or – of about 0.5 %, and these are far too expensive and delicate for such an application.  But, for what they are and do, the automotive fuel consumption computers work pretty well.

For older rigs or for those that did not come with one, there are many after market units that can be added.  The most popular one used in motor homes is probably the TripTek.  This is a plug-and-play computer that displays an overlay on the back-up monitor.  Most of the after market units are relatively easy to install if your vehicle was manufactured in the U.S. in 1995 or later.  All vehicles since then have included an OBD II (Onboard Diagnosis) interface connector beneath the dashboard.  This connector has all the information electronically that one of these computers requires.

Surprisingly, vehicles that are equipped with fuel monitoring displays attain much higher fuel mileage than those without.  This is due to operator awareness.  Put an ongoing readout of the average fuel consumption, in real time, in front of most people, and they will try to attain as high a reading as they can.  This will happen after each reset of that day’s run and after fueling up.  It may, in some cases, add a measure of increased safety related to a reduced highway speed that may be sought in an effort to get a higher reading. 

Some coaches come with a chassis OEM readout that monitors some of this information.  They generally only have one resettable MPG and one lifetime.  Whereas the addition of a TripTek, or similar system, can provide up to three resettable readouts, today’s run, trip leg and entire trip duration.  I personally use the “Leg” page to show readings since last fuel.  This page then gives me the total road miles miles, the MPG, and the average speed since I last filled the fuel tank.

So, do you have a fuel consumption readout on your RV or tow vehicle?  If so, do you find it a valuable tool?

Looking At Another Driving Aid      –      Lug_Nut      –       Peter Mercer

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  1. Ross

    I find that the best instrument that I installed was a vacum guage.I find that in my Ford V10, I try to run a lite throttle. And going up hill, turn cruise off, keep a light pedal and run at 3600 rpm for maximum horsepower.
    When I keep the vacum to 10 or higher, I know that is the best mileage I will get.
    I did install Airtabs on my Chateau, this really helped when its windy, or a 18 wheeler is passing. They helped the mileage some also.
    I also installed the Banks system, I received more HP and torque.
    The transmission doesnt now hunt back and forth for the right gear going up hill.
    As I realized that the factory instrument panel is actually “idiot guages”, they are indicators that something is happening, but not actual conditions. I had a volt meter, engine water temp guage, transmission temp guage, and the vacum guage installed.
    Watching the RPM’s and vacum guage, I know where my gas mileage is.

  2. Jay Sigel

    I have a Spartan chassis under my 2006 38′ Travel Supreme with both instantaneous and average MPG displays. The average read-out is about 7.3 but my actual mileage is usually less, about 6.5, when calculating gallons used during the fill-up. I’m also not that sure if I’m filling up the tank the same amount each time – it seems I can always squeeze in another 5 gallons if I’m patient.

    I tried to see whether driving at 65 MPH instead of 70 saved a significant amount of fuel, but the instantaneous MPG display varied tremendously depending on terrain and wind conditions, going from 3 to 99 MPG! It would vary somewhat even on level highway. I have been surprised that it didn’t seem to make any difference if I towed my Saturn SL2 or not as far as fuel consumption was concerned. Most of my trips are cross country and I don’t have the time luxury to drive slower than the speed limits. I set the cruise control and hope the wind is always behind me. In the summer, when my wife starts giving me “the look” as the temperature up front gets over 90, I know it’s time to turn on the generator and power up the roof airs. So, what are you gonna do? Our fuel consumption is what it is – it’s a motorhome, not a Prius!

  3. Kane Stachowicz

    I travel from Winnipeg to Palm Springs Ca. with our 2003 Windsor,8.8 l Cummins,6sp Allison with a trip tek computer. I calculate mileage manually and it seems to be the same as the computer. The only thing that I might do different is that I calculate the mileage after our 5000 mile trip. I travel at 63 mph. there and back, I find that I average 9.3 mpg. There are times during the trip when I’ve gotten as high as 11.3 and as low as 7.2 but I find that over the course of the 5000 miles I’m getting a more realistic number. My two cents Smokeater75

  4. I,M the old fashion type Miles divided by Gallons thats my MPG I.L talked to one fellow RVer about MPG same rig lenght etc he told me he gets 14.5mpg I even installed a Banks System on mine and I got 10.7 mpg I think people give you higher MPG just to let you know there rig is just a little better than yours. {my Opinion}
    Great Article never ending Story.
    Keep on RVing




  6. nnedtono, I question its repeatability. There are varitables also with using the onboard monitors. The method used can not guarantee accuracy or 100% repeatability. To do this and compensate for the many varitables the monitor would cost more than the car. Well, maybe that’s an overstatement, but, they are really not 100% accurate. They do however, give you a relative reading that can provide good information when compared to previous tank readings. Thank you for your valued input.

  7. nnedtono

    What makes me wonder about accuracy is I just purchased a 2011 Ford Super Duty and the manual claims that the Average MPG is accurate and if you calculate it on paper you won’t get the same answer because of how you refueled. I read it several times and it states that there are a lot of variables when refueling. I do try to get the best ampg by watching the gauge. So it does help.

  8. John, I’ve never checked, but is that driver information center resettable as far as the MPG goes? Also, let’s hear about the other one you have and as to how it works. Thanks for your always great input.

  9. John

    Hi Lug_Nut,
    I also have the driver info center on my ’08 Travel Supreme Alanté.
    So far I like it, can check turbo boost, engine & trans temps, avg MPG and instant MPG and more. Also have another monitoring system that I haven’t had a hance to check out yet. Has monitor alarms built in if you want them active. Will update you on the system once I have a chance to readup and try it out.


  10. John

    Hi Lug_Nut,
    I also have the driver info center on my ’08 Travel Supreme Alanté.
    So far I like it, can check turbo boost, engine & trans temps, avg MPG and instant MPG and more. Also have another monitoring system that I haven’t had a hance to check out yet. Has monitor alarms built in if you want them active. Will update you on the system once I have a chance to readup and try it out.

  11. Lug_Nut

    Tireman9, The Scangage has been a popular choice, and you probably indicated why, it is easy to install, a virtual plug and play. Thanks for your valued input.

  12. Tireman9

    I have a ScanGage II in my Coachmen Freelander. Easy to install as all I needed to do was to plug into the OBDII outlet. Got numerous of readouts to choose from. I Currently have MPH, %Load, RPM and instant MPG. At the end of the day I can check the average MPG for the days travels.
    I find that the Average is about 1 mpg low based on cumulative miles driven (5000+) and total gas purchased over two years.
    I am not worried about the error as I find the relative fuel usage is a good guide to help me keep my foot our of the gas.
    When climbing hills I can shut off the cruse before the engine shifts. When just driving down the road I can immediately see the relationship between speed and MPG.

    Most important the MPG / MPH relationship can change drastically based on wind direction and terrain.

    I believe that one of the reasons I can report 11.2 MPG is because of the use of this equipment.

    Another feature is I can use it in my car if I wish.

  13. John Massengale, That is great that you can use the Scangage in two vehicles. It’s not surprising that it is more accurate than the normal dash guages. Thanks for taking the time to share your information and experience.

  14. John Massengale

    I have a 02 bounder gas and I use a scangage. It has a number of different function on it but I lie the MPH, Temp, MPG and the RPM. I have noticed that the scangage is a little mor accurate than the dash gages I switch it from my mh to my jeep during the winter and use in the jeep. It is easy to program and has way more options than I every use..

  15. Art, Yes, that is one way to look at it, however most people do like to know. Attaining better mileage increases the overall fuel range, saves money and reveals some information on how the coach is running. If you were to drive long distances in very non-serviced areas, you would probably like to have that bench mark to properly guage your range. But, thanks for sharing your view with us.

  16. Lee Ensminger, Some of the Spartan definately have “Average MPG” in that service screen. You can change the reading that appear in the window to different pages. So instead of the info displayed now on the available four or so pages you can change it. It requires programming, not simply pushing the button to flip to other info. Yours probably will too. Check your manual or call Spartan. Thanks for your input.

  17. Don Jones, I was not aware that TripTek did not have a gas model. There are other brands sold through large auto distribution centers that seem to be relatively popular. Thank you for your input.

  18. Art

    My DP doesn’t have a fuel monitoring gadget and I really don’t want one. When the fuel gauge reads around 1/4 I fill her up, it’s as simple as that!
    Being RETIRED from the Engineering field where I did lots of calculating of all kinds of widgets it’s time to relax and enjoy the scenery. Does it REALLY matter if you get 8.5678 MPGs virus’s 8.9432………………I don’t think so. If so, maybe it’s time to by a hybrid MH or walk to the Grande Canyon. 🙂

    Now an acturate fuel gauge is another story. I had one go bad and it was a PIA. I was able to replace it myself with a little help from the fuel gauge supplier.

  19. Lee Ensminger

    I enjoy watching mine, although there is a problem. It only provides instant, or “right this second” fuel economy. Pretty depressing to see it drop to 1.7 mpg on starting up from a light, or on a hill. Then when coasting it goes to some fantastic figure of over 40 mpg followed by xx.x because it can’t display the hundreds of mpg it thinks I’m getting going down a hill at 60 mph with the throttle closed. It’s in a Travel Supreme MH on a Spartan chassis and called a “Driver Information Center.” It shows other things like oil pressure, speed, turbo boost, coolant temperature. Neat stuff. But I wish it had the ability to display AVERAGE mpg. Anyone out there know a setting I’m missing? Thanks.

  20. Don Jones

    I checked the Trip Tek web site and they state they do not make a unit for gasoline engines, where you aware of this.
    Thanks for the articles