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Thread: 90 recreational vs 100 LL

  1. #1

    Join Date
    May 2015
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    Default 90 recreational vs 100 LL

    Using 90 oct recreational fuel ethanol free lead free. Have to Lean aggressively on take off and cruise to get rpm up and stop roughness. Cht good. No overheating. Static rpm leaned about 2300rpm. About 2100 not leaned Better served by 100 LL?
    Thanks for your input.
    All the best!
    Bob Hubbard



    Sent from my iPhone using ShortWingPipers.Org mobile app

  2. #2
    Wag-builder's Avatar
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    Jan 2015
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    Charlotte Hall, Maryland
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    Default Re: 90 recreational vs 100 LL

    Bob,

    You did not day where you are located or what engine you have. My O-320 no suffix was certified to run 80/87 octane fuel so I would not expect to see that much difference running 90 octane. The higher the octane the slower the burn rate, so I would expect to see more RPM and slightly higher temps on 90 vs 100LL. So give us some more information, like field elevation, outside temp, engine/ prop, static RPM with 90 vs 100LL.

    Steve

  3. #3

    Join Date
    Oct 2013
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    northern Illinois
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    Default Re: 90 recreational vs 100 LL

    I have the STC for auto fuel. 150 hp tripe. I run the recreational ( clear ) fuel, it averages 90 to 93 octane depending. but never less than 90 octane. I buy 55 gallons at a time and normal about same cost as premium. My plane flys great with it, starts easy, temps are constant, plugs are always clean and look like new. I only run LL100 when I am fueling at other airports. Compaired to our local fuel costs I get more time in the air for the money.

  4. #4

    Join Date
    Feb 2010
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    Eufaula, OK
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    Default Re: 90 recreational vs 100 LL

    Where do you buy recreational fuel? I can buy 87 octane alcohol free at the gas station. Premium here is supposed to be alcohol free but it fails the water bottle test when I check it.
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  5. #5

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    Oct 2013
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    northern Illinois
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    Default Re: 90 recreational vs 100 LL

    I buy recreational fuel in Wisconsin. It is sold at several of the gas stations. Being from Illinois I just buy it a 55 gallon drum at a time.

  6. #6
    Jim's Avatar
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    Nov 2007
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    Fennville, MI
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    Default Re: 90 recreational vs 100 LL

    Hi Jeff,

    May, or may not, be current.
    https://www.pure-gas.org/index.jsp?stateprov=OK
    Our Michigan pumps use red handles.
    Last edited by Jim; 06-11-2019 at 08:21 PM.
    EAA Technical Counselor #4562
    Experimental Aircraft Association #140897 (1977)

  7. #7

    Join Date
    Feb 2010
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    Eufaula, OK
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    Default Re: 90 recreational vs 100 LL

    That's a good link. Even if some of it may not be current it has the means to make it current. I never bought fuel at the ones listed in my area but I know of 2 more where I buy 87 octane on a regular basis. One of which only sells road diesel, farm (red) diesel and 100% gas. The bad thing about 100% 87 octane gas here is it is the same price as premium.

    The store that advertises 100% premium, by way of a big sign on the curb, tested bad after pumping 5 gallons into my pickup. They use a single hose pump and I thought 5 gallons would clear the hose but apparently 5 gallons wasn't enough (now I know why my Harley never seemed like it run right. It required premium and it wasn't getting any). I ended up driving the 40 miles each way to get 100LL. Rumor has it the city is finally going to get fuel at the airport. It will be nice to not have to haul fuel from afar or siphon from one airplane to another to get a little fuel for an engine run or test flight after extended maintenance.
    "Good judgement comes from experience, and experience comes from bad judgement." - Fred Brooks

  8. #8

    Join Date
    Dec 2015
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    Default Re: 90 recreational vs 100 LL

    What sucks is swift 94 is more expensive than 100ll, I run 100ll in everything now. Like the unleaded but cash talks.. no reason to charge ga 5 bucks a gallon
    Last edited by SMO22; 06-12-2019 at 10:17 AM.

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