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Thread: Auto gas stc

  1. #1
    OVEREASYGUY's Avatar
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    Auto gas stc

    My pa-18 has an stc for autogas.
    engine was overhauled & I assume the stc remains.
    Recently I put a new carburetor on. Does that change anything? Are new carburetors built to withstand ethanol?

    When they say I have stc for auto gas does that mean gas with ethanol is ok? Im going on floats this summer & built a super cool fuel trailer. Id love to be able to run Autogas from the local gas station.
    your advice would be greatly appreciated.
    cliff dow jr in maine
    54ME cliff dow airport
    dow.us

  2. #2
    cubdriver2's Avatar
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    I've burned over 1000 gl of ethanol mogas. Half of it untreated. If your stuck and have to buy it use it up as fast as you can, if it sits it will absorb water and loose BTUs. Best thing is to carry the Startron and treat it when you buy it.

    Glenn
    Last edited by cubdriver2; 04-11-2022 at 09:58 AM.
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    akavidflyer's Avatar
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    Read the STC. Pretty sure it will EXCLUDE the use of ethanol fuels. It is in great big letter on the Peterson website. DO NOT USE FUELS CONTAINING MOONSHINE (ethanol)
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    hotrod180's Avatar
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    Read the STC.
    The EAA STC I for my C180 (EAA) says "do not use fuel that contains alcohol" about 4 times in the installation instructions.
    And the required placard adjacent to the fuel caps says that.
    As I recall, the Petersen STC that I had for a previous airplane has similar language.
    From the EAA STC:
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    Cessna Skywagon-- accept no substitute!
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  5. #5
    180Marty's Avatar
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    If your stuck and have to buy it use it up as fast as you can, if it sits it will absorb water and loose BTUs.
    Sealing the vent off with bread wrapper plastic and the twist tie helps keep moist air from coming and going. A small balloon would work too.

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    akavidflyer's Avatar
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    Quote Originally Posted by 180Marty View Post
    Sealing the vent off with bread wrapper plastic and the twist tie helps keep moist air from coming and going. A small balloon would work too.
    seems like a brilliant thing to do on a plane. What could go wrong...
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  7. #7
    RVBottomly's Avatar
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    Quote Originally Posted by hotrod180 View Post
    Read the STC.
    The EAA STC I for my C180 (EAA) says "do not use fuel that contains alcohol" about 4 times in the installation instructions.
    My EAA STC says the same thing. Even sent a little jug with instructions on how to test to see if ethanol is in the fuel.

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    Cliff with your million dollar budget just fill the thing with avgas, quit trying to cheap out.
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    For the last three weeks here in sunny Socal Avgas has been cheaper than regular car gas.
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  10. #10
    jnorris's Avatar
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    Quote Originally Posted by RVBottomly View Post
    My EAA STC says the same thing. Even sent a little jug with instructions on how to test to see if ethanol is in the fuel.
    EVERY EAA STC will say the same thing. No ethanol is allowed (or any form of alcohol for that matter).

    To the OP's original question, if you rebuilt the same engine to the factor specification your STC will still apply. And as long as the replacement carburetor is the stock spec, you're good. (No rubber tip float needles though!)

    If you replace the engine with a different serial number (and you have the EAA STC) you need to notify EAA of the serial number change, and have a new Form 337 filled out by your mechanic to apply the STC to the new engine. This assumes that the replacement engine is the same stock specification as the engine that the STC was originally applied to.
    Joe

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  11. #11
    hotrod180's Avatar
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    Quote Originally Posted by jnorris View Post
    .......If you replace the engine with a different serial number (and you have the EAA STC) you need to notify EAA of the serial number change, and have a new Form 337 filled out by your mechanic to apply the STC to the new engine. This assumes that the replacement engine is the same stock specification as the engine that the STC was originally applied to.
    I went through this a couple airplanes back.
    Can't recall if I had the EAA STC or the Petersen,
    but the deal was that they issued a new STC for the new engine s/n.
    They charged me the difference between the old price (buck a horsepower) and the new buck and a half).
    Cessna Skywagon-- accept no substitute!

  12. #12
    hotrod180's Avatar
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    Quote Originally Posted by bob turner View Post
    For the last three weeks here in sunny Socal Avgas has been cheaper than regular car gas.
    On a somewhat related subject,
    I saw in the news that federal regs were changed to allow E-15 gasoline to continue to be sold into the summertime.

    Biden will allow summer sale of E15 gas : NPR

    I'm wondering if this latest thing will effect the availability of ethanol-free mogas?
    Cessna Skywagon-- accept no substitute!

  13. #13
    jnorris's Avatar
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    Quote Originally Posted by hotrod180 View Post
    I went through this a couple airplanes back.
    Can't recall if I had the EAA STC or the Petersen,
    but the deal was that they issued a new STC for the new engine s/n.
    They charged me the difference between the old price (buck a horsepower) and the new buck and a half).
    Must have been Petersen, because we didn't do it that way at EAA. I handled all the fulfillment for EAA Auto Fuel STCS for the last 3 years of my employment there (I retired this past June), so I know the process. A simple serial number change was no cost. The only time new STC paperwork was issued was when the STC had been originally purchased before 2004 (when the FAA updated EAA's STCs, which resulted in new STC numbers) And even then, it was just a $40 update fee, not the full price of the STC.
    Joe

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  14. #14
    hotrod180's Avatar
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    Quote Originally Posted by jnorris View Post
    ...A simple serial number change was no cost. The only time new STC paperwork was issued was when the STC had been originally purchased before 2004 (when the FAA updated EAA's STCs, which resulted in new STC numbers) And even then, it was just a $40 update fee, not the full price of the STC.
    I looked in my old notes, here's more details:
    the airplane (C150) had been issued a mogas STC back in the day.
    It had since been upgraded to a 150hp Lycoming-- so not a simple s/n change.
    I bought it in 2008.
    I wanted all the paperwork squared away, so I called the STC holder (still not convinced it was Petersen),
    to get a mogas STC for the new engine.
    I was charged the $75 difference between what was paid originally (100hp x $1 = $100)
    and what the current charge would be (150hp x $1.50 = $225).
    Cessna Skywagon-- accept no substitute!
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  15. #15
    jnorris's Avatar
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    Quote Originally Posted by hotrod180 View Post
    I looked in my old notes, here's more details:
    the airplane (C150) had been issued a mogas STC back in the day.
    It had since been upgraded to a 150hp Lycoming-- so not a simple s/n change.
    I bought it in 2008.
    I wanted all the paperwork squared away, so I called the STC holder (still not convinced it was Petersen),
    to get a mogas STC for the new engine.
    I was charged the $75 difference between what was paid originally (100hp x $1 = $100)
    and what the current charge would be (150hp x $1.50 = $225).
    That sounds about right. Not just a simple engine swap, but completely different make/model of engine (and more horsepower). I'm pretty sure both EAA and Petersen would handle that situation in the same manner.
    Joe

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