Poor gas mileage

Discussion in 'Touring Models' started by ryno, Jan 22, 2010.

  1. ryno

    ryno Member

    Hello folks,

    I've recently been getting some pretty (EDIT) mileage on my '08 FLHTP (103"). Its got 16k on the clock and a set of Rush slip-ons. I filled up today (91 octane, like always) and was getting about 28mpg (135mi to a tank) :( Now this is virtually all around town riding with quite a bit of idling/warming up since its winter. I've only had the bike a few months but I was expecting a little better mileage out of her. I am going to check the spark plugs first as that is my prime suspect at this point. I put a Ness Big Sucker on it this morning and am going to get the ECM re-flashed on Monday. Maybe this will help, too? Any suggestions appreciated.


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    Last edited by a moderator: Jan 22, 2010
  2. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    Smell any raw gas starting or stopping? No gas leaking out the bottom of the engine/tranny area, right? Then check the plugs, and as long as they are not black, wet and gooey, that may be what you get. My 88 ci gets around 32mpg. But you did not get a 103 ci engine for economy, right?

  3. ryno

    ryno Member

    Nope, no raw gas smell and it runs like a scalded ape. Perhaps a good 2-1 exhaust and a tune would optimized efficiency. Like you said, if I wanted fuel economy I would ride my wife's Vespa :D

    PS.. Sorry about the language, I was trying to keep it clean and didn't realize that it was still considered inappropriate.
  4. Hoople

    Hoople Account Removed

    Do you know if the previous owner installed an add on fueler or had the maps changed.
  5. ryno

    ryno Member

    The PO was the City of Amarillo/Police Dept. so I'm guessing it was pretty much left stock. It was "civilianized" before I bought it from the HD dealer that supplies them with the bikes. As far as I can tell I'm the only thats done any mods to it.
  6. Hoople

    Hoople Account Removed

    Does it have any historic codes in the ECM. Check to see if you have any O2 sensor related codes in it.
    On my '09, when you boot the ECM if the Check engine light goes off after 4 seconds and then comes back on, followed by it going off once again, it means it has historic codes in the ECM.
  7. Chopper

    Chopper Senior Member

    Here's something the factory sent me a while back concerning customers fuel mileage.

    In today's world of $3.00/gal fuel, gas mileage is on most everyone's mind. I get questions about fuel mileage on almost a weekly basis. To help customers understand the issue, I offer a bit of an explanation.
    First of all, it's important to remember that the manufacturer's stated mileage may not reflect your specific set of riding conditions. Tested bikes are operated in a controlled environment. On the road, the unique combination of environment and your personal riding style will produce varying figures.
    The following is a list of factors that affect mileage, usually in a negative manner:
    Topping the list is the operator's throttle hand. This is without a doubt the factor that affects mileage the most. The farther and faster you twist the grip, the more fuel will be used. A heavy throttle hand will use a lot of fuel.
    Wind is also a major factor in mileage. A headwind will cost mileage and a tail wind will increase mileage.
    Along with wind comes drag. Certain accessories act as a wind barrier, producing drag. A big touring windshield, while a necessity in reducing rider wind fatigue, has all the aerodynamics of a brick.
    If available for your bikes, consider a detachable windshield. Remove it when riding shorter distances or at slower speeds to increase your average fuel economy. If gas mileage is high on your list, keep drag in mind when choosing handlebars for your bike.
    Tall ape-hanger bars make the rider into a sail, contributing to your wind drag. Another factor that affects your bike's gas mileage is weight. Bikes that are fully loaded - rider, passenger, and luggage - will suffer a reduction in mileage. Your route. Stop-and-go traffic is less efficient than steady highway speeds. Steep grades will use more fuel than flat roads.
    Most performance modifications will reduce mileage a bit. However, installing an overdrive 6 speed gear set will get you more miles per gallon as well as less wear on your motor.
    Proper maintenance is important as well. A bike that is well maintained operates with greater efficiency, which will improve mileage. A dirty air filter, fouled plugs, or clogged fuel filter will all reduce your gas mileage.
    Lastly, you must check your mileage correctly. Fill your tank up. Record the odometer reading and ride until you need fuel. Again, fill the tank and record the amount of fuel needed. Divide the miles by the gallons and there's your answer. To obtain a reasonable average, you'll need to average five or six tanks.
    All in all, consider yourself fortunate to own a motorcycle. On average, bikes still get as much as two times the mileage of the average family sedan.

    This was send a few years back, I know their's a few cars out there now that put my scoot to shame, then again I only have two speeds, fast & faster, I also have been known to stop by a country & western bar once and a while to pick up a fat girl, quiting drinking has solved the later of my milage problems though:D
  8. glimmerman

    glimmerman Active Member

    mileage can vary considerably in cold months. RFG, reformulated gasoline is a nasty thing to use in winter months. i loose at least 5-8 mpg on my 01 rk police. stock 88 in. this is here in the mid atlantic region. try using only name brand gasoline and not the lower priced one stop shop places. other riders have said some here are using up to 15% ethanol in the gas. sure stretches the gas and has a lower btu rating (power output). which means more twisting for the same go. wait a few months and see what hot weather brings. maybe the unRFG won't be so irregular.
  9. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    Although chopper has coverd almost everything that could affect your gas mileage there is 1 other minor point to consider and that is correct tyre pressure

  10. Hoople

    Hoople Account Removed

    I agree with all of the above, but 28/ mpg sure is thirsty to me. Granted I have a 96 cu/in but I run totally open loop (no cells in the 14's) and get much better gas mileage than that. Got to probe the exhaust to know for sure. If the probe says you good, then your good.