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Thread: Autogas

  1. #1
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    Default Autogas

    The Rotax engine is designed to run in auto gas and I think 91 octane is the recommended octane. I live in Colorado, well above sea level. I normally put regular in my tank so I don’t remember the octane rating of “premium”, but I think it is 89 out here, and regular is 85 if I recall correctly. It also contains ethanol. What do all of you Rotax owners(who are well above sea level) use in your Rotax engines?

    Steve

  2. #2
    Senior Member Dave S's Avatar
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    Default Re: Autogas

    The term "premium" is purely a marketing term....which is best off ignored in favor of facts.

    Depends on which engine you have and how octane is labeled in your locale.

    The 80 hp 912 is a lower compression engine and can use 87 octane

    The 100 hp 912ULS requires a minimum of 91 octane

    With the octane being determined by the average value of the two methods of determining octane - research and motor, which you should see on the dispensing pump as R + M/2 = 87 or 91 (be aware there is other labeling which uses only one of the methods and the numbers come out differently)

    OK now the corn gas thing - Rotax permits up to 10% ethanol as far as the engine is concerned; however, you have to consider the entire fuel system. Kitfoxes use fiberglass tanks and I believe the consensus is fiberglass tanks can degrade with the use of ethanol. I have a friend with a different plane which has poly fuel tanks and he runs 91 octane corn gas all the time because the entire system is compatible up to 10% ethanol.

    Having a 912ULS in our kitfox, I use 91 corn free autogas, occasionally 100LL when on a trip when that is all a person can get. The autogas is also procured from a site which has a dedicated tank and pump for that product.

    One word to the wise - some (getting to be more all the time) auto fuel stations do not have a dedicated 91 octane pumps; but, use blend valves drawing from different grades of fuel all going through one hose and pump - this means the first gallon, even if you select 91 corn free, has a pretty good chance of being diluted wItith lower grade or ethanol contaminated junk. I have no idea how often blend valves can fail but I am not at all in favor of getting airplane fuel from any place which uses multiple tanks and a blend valve. One gallon of 87 in a 5 gallon container of gas (or a gallon of E85) which you want 91 octane in could very well inspire detonation in a 912ULS as the 91 is a hard minimum. I do know of folks who squirt the first couple gallons in their car then fill their aircraft cans.
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
    Senior Member Esser's Avatar
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    Default Re: Autogas

    Shell V Power 91. It’s almost the only ethanol free gas I can get. I haven’t run it in my Rotax yet cause I’m not flying but put it in the Cherokee for years.
    ------------------
    Josh Esser
    Flying SS7
    Rotax 914iS
    AirMaster Prop

    Edmonton, AB, CWL3

  4. #4
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    Default Re: Autogas

    As far as I know, we don’t have corn free gas as an option. I am headed down the hill in an hour to drop off daughter and then to the gas station to see what we have available. At Denver altitude, we don’t get full power out of any engine (car or otherwise) that isn’t turbo charged, so the available octane ratings are lower because we don’t need the higher numbers necessary at sea level to make most cars run as designed.

    And being so close to the smog laws in Denver, I believe ethanol is in all the gas, at least in the winter, when inversions trap the smog down low.

    I just hate the idea of running 100LL due to fuel cost and maintenance cost (time and money) for the engine.

    Maybe I should just hang a PT-6 on the front.

  5. #5
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    Default Re: Autogas

    Here is a link to a site that will tell you where you can get ethanol free gas in every state. Not garunteed to be accurate, as people can add gas stations to it if they wish, but it's a start. JImChuk
    https://www.pure-gas.org/

  6. #6
    Senior Member jiott's Avatar
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    Default Re: Autogas

    Maybe CO has an airport or two with clear Mogas on site? Oregon has two. Generally airport fuel tanks and dispensing equipment are cleaner and better maintained.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  7. #7
    Super Moderator Av8r3400's Avatar
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    Default Re: Autogas

    Hopefully this will all be academic soon. With the introduction of lead free aircraft fuel we won't have to worry about carting fuel from questionable auto-gas stations.

    There's a couple airports in my area that dispense Swift fuel. This is an excellent, if not widely available yet option.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  8. #8
    Senior Member jrevens's Avatar
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    Default Re: Autogas

    Steve,

    We do have enthanol-free gas here in the Denver area, but not a lot. There is a station in Lakewood that carries “premium”... I’m not sure of the exact octane yet. The Longmont airport (KLMO) carries it also. I’m like you, and don’t much like the prospect of using 100LL, but I will if necessary. I’ve been thinking seriously of buying a 30 or 40 gal. aluminum transfer tank to mount in the bed of my pickup under the tonneau cover, and using that to fuel my airplane with the “farm gas”. I find it ironic that many farmers need/prefer the alcohol-free stuff for their “off-road” vehicles. I’m hoping that in a year or 2 Swiftfuel or Shell will start to have their unleaded alcohol-free products (both are 100 octane or better) all over the country. I believe that Swiftfuel is available at a few airports in the midwest and Eastern parts of the country now. I know that Portage, WI (one of my favorite stops going into OSH) has it. Anyway, it’s going to get better... 100LL is definitely going away.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  9. #9
    Super Moderator Av8r3400's Avatar
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    Default Re: Autogas

    I believe that the mandate for unleaded aviation fuel is this year (2018).
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  10. #10
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    Default Re: Autogas

    Quote Originally Posted by jrevens View Post
    Steve,

    We do have enthanol-free gas here in the Denver area, but not a lot. There is a station in Lakewood that carries “premium”... I’m not sure of the exact octane yet. The Longmont airport (KLMO) carries it also. I’m like you, and don’t much like the prospect of using 100LL, but I will if necessary. I’ve been thinking seriously of buying a 30 or 40 gal. aluminum transfer tank to mount in the bed of my pickup under the tonneau cover, and using that to fuel my airplane with the “farm gas”. I find it ironic that many farmers need/prefer the alcohol-free stuff for their “off-road” vehicles. I’m hoping that in a year or 2 Swiftfuel or Shell will start to have their unleaded alcohol-free products (both are 100 octane or better) all over the country. I believe that Swiftfuel is available at a few airports in the midwest and Eastern parts of the country now. I know that Portage, WI (one of my favorite stops going into OSH) has it. Anyway, it’s going to get better... 100LL is definitely going away.
    As far as I know KLMO is the only airport within say 3 or 400 miles of Denver that sells mogas onsite. Really a PITA if you are considering mogas out here in the wild west!

    I believe that the mandate for unleaded aviation fuel is this year (2018).
    Don't hold your breath! Once Phase 2 testing is done there is a "6 month" period for the FAA and ASTM to write it up and then someone has to decide on the transition phase in and how it will be implemented. Knowing how "fast" these guys work, I'd suspect either neither the Swift or Shell products will be available any time soon.

    YMMV, Greg

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