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Thread: O-360 Marvin-Schebler Autofuel.

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    O-360 Marvin-Schebler Autofuel.

    Hello,
    I am planning to use auto fuel in my O-360 PA18. Does anyone have experience with that? I have the required hoses.. and above 500 ft I get vertigo so vapour locks should not be an issue...Does anyone have experience with the auto fuel?
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    cubdriver2's Avatar
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    Quote Originally Posted by jokerswe2008 View Post
    Hello,
    I am planning to use auto fuel in my O-360 PA18. Does anyone have experience with that? I have the required hoses.. and above 500 ft I get vertigo so vapour locks should not be an issue...Does anyone have experience with the auto fuel?
    Not an o360 but I have burned over 20,000 gls of efree in little Continentals

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Quote Originally Posted by cubdriver2 View Post
    Not an o360 but I have burned over 20,000 gls of efree in little Continentals

    Glenn
    the O-360 is approved for autofuel- so I’m most concerned about the carburetor. Does the continentals also use Marvin Scheblers?!

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    Quote Originally Posted by jokerswe2008 View Post
    the O-360 is approved for autofuel- so I’m most concerned about the carburetor. Does the continentals also use Marvin Scheblers?!

    Nearby flight instructor has run two Cessna 150s for years and hundreds and hundreds of hours on auto gas. The O200-A engines use M-S carburetors. Has not been a problem for him.
    You can't get there from here. You have to go over yonder and start from there.

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    BC12D-4-85's Avatar
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    Ran 92UL in an O-360 PA-12 when needed in summer. Did ok but preferred 20-25% 100LL if I could get it mixed. I think auto fuel contains more water and had some issues with ice crystals so ran 100LL in winter if available.

    Gary

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    skipster's Avatar
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    I ran super un- leaded in a 0-360A1A in a Starduster Too without any problems in the 200+ hours we had it

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    You will be all right. I have an O-320 with MS carb no problem after couple thousand hours. I run mostly ethanol laced 89 straight from the pump. Just watch your engine temperatures and don't expect 100LL performance. If you are not flying often keep a bit of avgas in second tank (if you have one) and before engine shutdown "fill the fuel system" with avgas.

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    I believe on the o-360 you must use premium, however these days it is about the only ethanol free fuel you can get in the states.

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    Gordon Misch's Avatar
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    From the Peterson Auto Fuel STC website:

    "Approved Engines & Airframes
    Auto Fuel STCs are approved on 48 different engine types and 100+ airframes including nearly all 80/87 octane engines and the majority of airplanes in which these engines were installed. Several high compression engines are also approved for the use of 91AKI auto fuel including the 180 horsepower 0- 360 and the 115hp (or less) 0-235-L2C. "
    Gordon

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    Hardtailjohn's Avatar
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    The carburetor float level should be set for the specific gravity of the auto gas, as it's different than the specific gravity of av gas. The carburetor manual will tell you the specifics.
    John
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    cubdriver2's Avatar
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    Quote Originally Posted by Hardtailjohn View Post
    The carburetor float level should be set for the specific gravity of the auto gas, as it's different than the specific gravity of av gas. The carburetor manual will tell you the specifics.
    John
    I have switched back and forth on 5 different aircraft and never notice any difference in performance.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    Quote Originally Posted by electricsnail View Post
    I believe on the o-360 you must use premium, however these days it is about the only ethanol free fuel you can get in the states.
    I've used 87 octane unleaded e-zero mogas in my airplanes for years,
    from the local Cenex aka Co-op farm stores.
    I've burned over 3000 hours worth of that fuel in O200's, O300's, O320's, and O470's--
    mainly mixed with 20-25% 100LL.
    No problems with MS carb, or anything else.
    Cessna Skywagon-- accept no substitute!
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    If your fuel tank has any sloshing compound or other seam sealer, you want to be careful. I have been running 3/4 auto for maybe 40 years, but won't put it in my wing tank for that reason.

    It could be better now; stuff like MTBE is no longer allowed in auto gas.

    A lot of folks tell me modern auto gas is bad for Cubs, and even old cars, but I don't seem to have any problem going well beyond TBO.

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    Quote Originally Posted by cubdriver2 View Post
    I have switched back and forth on 5 different aircraft and never notice any difference in performance.

    Glenn
    Just telling you what the carburetor manufacturer says.... Nothing personal, but I'll stick to their advice.
    John

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    Gordon Misch's Avatar
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    Back and forth between Avgas and 90 octane Mogas in my 160 HP doesn't seem to make any difference in performance. Digital tach, with 10 RPM resolution.

    Didn't change anything with the carb when converting from 150 HP. Best power (sea level) is with the mixture pulled out about an inch.
    Last edited by Gordon Misch; 03-17-2019 at 11:09 PM.
    Gordon

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    skywagon8a's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    I have switched back and forth on 5 different aircraft and never notice any difference in performance.

    Glenn
    Glenn, You are near sea level, John is 4000 msl perhaps you would notice a difference at that altitude?
    N1PA
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    cubdriver2's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Glenn, You are near sea level, John is 4000 msl perhaps you would notice a difference at that altitude?
    I'm at 1340 so your probably right

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Steve Pierce's Avatar
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    I burn almost all e-free mo gas but don't let is sit. Mo gas goes bad long before 100LL and mucks things up.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers
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    What about the injected variants - I have an IO360 A1A and really struggle to get 100LL

    Regards
    Marc

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    sjohnson's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    I burn almost all e-free mo gas but don't let is sit. Mo gas goes bad long before 100LL and mucks things up.
    Does autogas help with lead-fouling? I get some fouling on the bottom plus, even though I lean on the ground.
    Idaho drinks more wine per person than any other state in the country.

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    Quote Originally Posted by sjohnson View Post
    Does autogas help with lead-fouling? I get some fouling on the bottom plus, even though I lean on the ground.
    Mogas is lead free

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

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    Quote Originally Posted by sjohnson View Post
    Does autogas help with lead-fouling? I get some fouling on the bottom plus, even though I lean on the ground.
    Yes being there is no lead in the fuel. My experience is that it is rare to have valves sticking in the guides as well.
    In general any of the lower compression engines that were not originally rated for 100Oct fuel is better off on autogas.
    Obviously opinions vary.
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    TurboBeaver's Avatar
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    Quote Originally Posted by CharlieN View Post
    Yes being there is no lead in the fuel. My experience is that it is rare to have valves sticking in the guides as well.
    In general any of the lower compression engines that were not originally rated for 100Oct fuel is better off on autogas.
    Obviously opinions vary.
    When we where "fish spotting" back in the 90's, our boats brought us "car gas" to burn in our Cubs.
    Most of us found that a steady diet of straight "unleaded" regular auto fuel in
    0320 engines will most certainly result
    in valves starting to "drag" in the guides. If you persisted the valve timing would get so far off the ignition timing they would start to sound like a
    "Patridge drumming up on the ridge"
    All that was easily cured by adding 1 quart of Marvel Mystery Oil to 55gals of auto fuel. Never experenced ANY problems with auto fuel as long as it had the MMO as an additive!
    Pretty common to go through 30/40 drums of fuel every season .
    The MMO most certainly effects the valve stems relationship to the guides.
    Of course blending in a small amount of lead via AV gas is also an excellent
    choice, and we found that as little as 10% was sufficient for valve lubrication! Your mileage will likely vary.............

    Sent from my LM-X210 using SuperCub.Org mobile app

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    sjohnson's Avatar
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    Quote Originally Posted by cubdriver2 View Post
    Mogas is lead free

    Glenn
    Doh. Of course.

    What I should have asked is whether occasional use of auto fuel, but majority use of avgas, will help with lead fouling.

    Thanks,
    Steve
    Idaho drinks more wine per person than any other state in the country.
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    TurboBeaver's Avatar
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    Sjohnson,
    I am guessing a good way to answer that question is NO a little bit of auto
    fuel will not cure your leading problems in your lower plugs........
    Straight auto fuel will cure that problem. But with out MMO it can cause other
    problems, a lot of guys think that 100LL is actually low in lead; however that
    may be true compared to 130, but I think it's way more than the original 80/87
    these old engines were designed for.
    Possibly Pete can comment on this to clear it up even better?
    What say you Sky8A???
    E

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    cubdriver2's Avatar
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    Quote Originally Posted by TurboBeaver View Post
    Sjohnson,
    I am guessing a good way to answer that question is NO a little bit of auto
    fuel will not cure your leading problems in your lower plugs........
    Straight auto fuel will cure that problem. But with out MMO it can cause other
    problems, a lot of guys think that 100LL is actually low in lead; however that
    may be true compared to 130, but I think it's way more than the original 80/87
    these old engines were designed for.
    Possibly Pete can comment on this to clear it up even better?
    What say you Sky8A???
    E
    100LL has 5 times the lead that 80 had

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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    They call it 100LL since there previously had been a higher lead content in 100 oct fuels not to mention the even higher octane fuels developed in the '30s & 40s.
    Today's unleaded fuels are pretty good as long as the ethanol is kept in a separate glass.
    And yes Marval Mystery oil is good stuff, less needed in little Continentals than Lycomings.
    Lycoming engines do better with more oil flow to the valve cover especially the exhaust valve.
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    TurboBeaver's Avatar
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    Tnx Glenn, could not remember how much more lead was in 100, but knew it was huge!
    So that should clear up any concerns on plug fouling, your running "5 times" what the engine
    was designed to deal with when you run straight 100LL. So if the math is correct, running 50%
    auto fuel/ 50% 100LL Av gas. Your still 2.5 times what 80 had in it ???

  29. #29
    skywagon8a's Avatar
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    I'll try. The following contains a table of aviation fuel grades: https://en.wikipedia.org/wiki/Avgas
    Notice that 80/87 oct contains 0.14 g/l of lead. 100LL contains 0.56 g/l of lead. and 100/130 contains 1.12 g/l of lead which was double that of the current 100LL. AND the current 100LL contains 4 times the amount of lead as the old 80/87 oct.

    sjohnson, Since you are fouling just your bottom plugs it appears that you should increase the heat range of your bottom plugs. Search on line for a spark plug chart for the information for your brand of plug.
    This has some information which you may find informative. http://www.imps4ever.info/tech/engin...ark-plugs.html " A hot running plug has a much slower rate of heat transfer and is used to avoid fouling where combustion chamber or cylinder head temperatures are relatively low."
    N1PA
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    Bugs66's Avatar
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    Over 500 hours on my O-360-A1A with probably 90% mogas 91E0. No issues ever. Clean plugs. I only run avgas on cross country when no other choice.
    Bugs
    http://www.supercubproject.com
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    Way back in time the O-235 powered trainers fouled lower plugs weekly. We started adding TCP to the 100LL and that pretty well cleared the problem up.
    The TCP would hold the lead in suspension with the lower flame temps in the low compression engines. This allowed the lead to be carried out the exhaust instead of collecting on the relatively cool cylinder head where it ran down and puddled on the lower plugs.
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    hotrod180's Avatar
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    Quote Originally Posted by sjohnson View Post
    ….What I should have asked is whether occasional use of auto fuel, but majority use of avgas, will help with lead fouling. ..
    IMHO the less lead you burn, the less lead fouling you'll have.
    But occasional use is kinda like taking an occasional blood pressure or cholesterol pill--
    probably not gonna help much.
    You'd be better off with occasional use of 100LL, but majority use of mogas.
    Some folks don't like messing with jerry cans, etc,
    but I've been fueling with them for so long I prefer it to screwing around at the fuel pump.
    Some airports offer mogas, usually 91 or 92 octane (aka premium),
    but there's usually not much price difference from 100LL.
    In fact, according to airnav.com, 100LL is $5.00
    at KAWO's Arlington Flight Service
    vs $5.15 for mogas
    My own cost is around $3.25 for 87 octane mogas, vs about $5.50 for 100LL at my airport.
    Cessna Skywagon-- accept no substitute!

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    Quote Originally Posted by Bugs66 View Post
    Over 500 hours on my O-360-A1A with probably 90% mogas 91E0. No issues ever. Clean plugs. I only run avgas on cross country when no other choice.
    Hi Bugs

    do you ever have problems starting when your engine is hot?
    do you have a return to tank on your injection system?
    which compression pistons you running?

    best regards
    Heiko

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    Bugs66's Avatar
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    Quote Originally Posted by bodumatau View Post
    Hi Bugs

    do you ever have problems starting when your engine is hot?
    do you have a return to tank on your injection system?
    which compression pistons you running?

    best regards
    Heiko
    Heiko,
    I have never had a single incident or problem on startup related to fuel system ever. I've flown my Cub in OAT low as ~8*F and high as ~102*F. I run the typical dual pickup (Cub Crafters style) headerless fuel system. I have standard O-360 8.5:1 compression.

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    Interestingly Lycoming does not allow automotive fuel below 93AKI for their engines:

    https://www.lycoming.com/sites/defau...ed%20Fuels.pdf

    https://www.lycoming.com/content/unleaded-fuels-part-1

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    Quote Originally Posted by AKClimber View Post
    Interestingly Lycoming does not allow automotive fuel below 93AKI for their engines:
    Consider their lawyer speak, take an engine engineered to be safe on 80 Oct fuel and now require 93 or more if unleaded, which is not available in many parts of the country. Kind of makes it sure they will not accept any warranty or liability.

    Yet when a valve sticks in the guide generally due to poor material selection and aggravated by the lead content. And this suck valve takes the plane down generally with loss of life, where are they?

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    BC12D-4-85's Avatar
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    Where are they in valve sticking? They are suggesting via SB 338C or ? a time specific exhaust valve wobble test and if required a guide reaming. No Golden Parachute for some.

    Gary

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    Quote Originally Posted by BC12D-4-85 View Post
    Where are they in valve sticking? They are suggesting via SB 338C or ? a time specific exhaust valve wobble test and if required a guide reaming. No Golden Parachute for some.

    Gary
    The major part of EX valve sticking has to do with lack of oil flow to both cool and lubricate the guide and stem.
    A secondary issue is buildup of lead in the guide. This is more of an issue in low compression engines where the lack of oil flow has shows itself as the culprit with higher powered engines.

    We should do a call out to those that have lived exclusively with Mogas, my experience was mostly with an O-200 which was Mogas only with a flawless experience. Glenn G has chimed in with a long and comfortable history with small Continentals.
    Local people I know who have been dealing with sticking valves I have talked into hauling Mogas in, they are impressed how much better their plane runs.
    This may not be for everyone and my experience for the most part was being one of the first to buy the STC back in the '80s. Today's auto fuel is not even close to the ASTM 439 that was originally specified in the beginning but there is nothing wrong with the fuel today as long as you keep the ethanol out.
    The issue with ethanol has nothing to do with flight parameters but to do with the rubber and plastics used in our planes as well as any older vehicle. This pertains to hoses, diaphragms in fuel pumps and other soft parts in the fuel system.

    You should look up what Ducati went through when it's fuel tanks swelled when the fuel changed, their replacement tanks failed just as quick, no clue how much that cost them.
    In the race cars I build the fuel bladders were going stiff with a result of failing. At first the manufacturers changed to stupid short life cycles till the formulation of resins used was changed.
    I am quite sure the bladders in aircraft would fail as well but most of them are feeding higher power non auto fuel eligible engines.

    The SB 338C is just another, Their way of saying our engineers have once again F'ed up and you need to pay for it. I do not see that they have made any production changes to cure the issue.
    Every batch of Lycoming crankshafts still need a material sample sent to an independent lab for material evaluation. So much for the problems being solved. There are not many companies forging the cranks and we have recently seen more cranks pulled from service.

    Personally now that the Chinese are building a new Continental factory down south with a very clear statement that they are not intending to build the same product we have been living with. Get ready for a new line of heavy fuel engines for our use.
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  39. #39
    hotrod180's Avatar
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    Quote Originally Posted by AKClimber View Post
    Interestingly Lycoming does not allow automotive fuel below 93AKI for their engines:

    https://www.lycoming.com/sites/defau...ed%20Fuels.pdf

    https://www.lycoming.com/content/unleaded-fuels-part-1
    Link #2 is what I'd call a memo or informational article- certainly not regulatory IMHO.
    Link #1 is a service letter-- compliance is not mandatory for part 91 as I understand it.

    Curious if an FAA-approved STC (for 87 octane or 91 octane mogas) trumps the manufacturer's recommendations.
    Last edited by hotrod180; 03-27-2019 at 10:45 AM.
    Cessna Skywagon-- accept no substitute!

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    That Lyc service letter looks to be a study for replacing 100LL, From page 2

    First, notice that we specified 93 AKI as the octane level. This octane level provided the required detonation margin without modification of our engine FAA Type Design allowances, including cylinder head temperature limits. 93 AKI is "Super Premium" fuel. That AKI rated octane is what is needed to achieve the exact same power performance on the approved engines as 100LL avgas. 93AKI is produced worldwide, but not necessarily distributed worldwide.

    I have not read page 3 or later yet but our discussion for lower powered engines that were rated for 80 or even 91 oct is not the same as the need for a 100LL replacement.

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