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Thread: MOGAS stc

  1. #1
    Member Daveintheburbs's Avatar
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    Default MOGAS stc

    What are the less obvious pros and cons to this mod, specifically in Cessna 172- 185 continentals or lycoming conversions.
    Thanks,
    Dave

  2. #2
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    Here's a less obvious one. Car gas stinks. I mean it really smells bad. It smells up the truck with the tank and it smells up the plane that burns it. I have some 50/50 avgas/car gas in my tank right now. It must be that car gas has more vapor pressure or something because I can smell gas from 30 feet away. I never had that problem in 15 years of straight avgas in that tank.

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    Member martentrapper's Avatar
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    I suspect there is alot of info on the internet about this. Plus info from the engine makers themselves. You might also walk into an overhaul shop in Anch. (aerorecip) and ask them about it. I'm sure they tear down plenty of engines that were run on mogas.
    I'm pretty sure all engine maker and overhaul shop warranties are voided by the use of mogas.
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  4. #4
    Member Float Pilot's Avatar
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    I used to have a couple of Cubs that burned Mo-Gas. Plus My current Cub has had plenty of Av-Gas and Mo-gas in a 50-50 or 30-70 mix.

    One point is that car gas is no longer that much cheaper.

    Another point is that more and more alcohol is being put into car-gas. (just to help the politicians in the crop growing states, since it actually takes more energy to make the alcohol than it produces)
    Alcohol is very bad in Avaition use. It attracts water and bonds with it.

    Car gas does not have any lead, which is what you need to provide some top end lube effect. So most gas gas users also have to use Marvel Mystery oil added to their Mo-Gas.

    There are also some other weird additives included at certain times of year or in certain states (Calif), these tend to eat gaskets, O-rings and some carb parts.


    On the postive side, some lower compression engines (C-65s, C-85s C-90s, 0-235, 0-290s, 0-300, 150 hp 0-320s) run better with a little less octane, so mixing the gas helps the valves from being blow-torched and the plugs from fouling as fast.

    Anything from 160 hp on up really should have Av-Gas.
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  5. #5
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    Default Grizzly 1

    Quote Originally Posted by Daveintheburbs View Post
    What are the less obvious pros and cons to this mod, specifically in Cessna 172- 185 continentals or lycoming conversions.
    Thanks,
    Dave
    Hi Dave,

    All these guys are right, of course. In the long run, though, why not just install an EGT gauge and a verier mixture control? Works wonders, even on a 150-Super Cub.

    Proper mixture at all times, even during takeoffs. As for leaning out to save a buck or two, the system can't be beat. Also extends engine life. Seems that the fuel savings during takeoff, climbout and cruise will soon pay for both the EGT and the mixture control (which isn't complex), and will continue to promote a little pocket money along the way.

    Regards

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