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The ICON A5 POH gently implies, and other sources outright claim, that its Rotax 120iS prefers a diet of 87 octane mogas, and I've found a couple of sources claiming that while it'll take 100LL, the lead builds up in the oil, requiring more frequent oil changes.

The POH itself says that you should be mindful of vapour-lock, especially at higher altitudes or hot air temperatures. They suggest a blend of mogas and avgas is a good practice when in doubt.

Obviously if you've folded the wings and put your flying jetski on a trailer, you can probably top up the tank at any gas station, but as I'm preparing to simulate flying the Appalachian Trail, including a staging flight from Massachusetts to Georgia, it occurs to me that the trailer stays at home.

So when you're on tour, flying the thing airport to airport, if you want to use mogas.... where do you even get it? Do airport fuel stations commonly have mogas available? If so, how is it usually priced and can you tell which places would have it from sources like Skyvector?

Or is this a case of "bring a few jerry cans and expect to hike to and from the nearest gas station?"

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    $\begingroup$ What type of airports are you going to be flying into? Small, local fields with lots of ultralights and microlights are much more likely to have mogas on hand than if you fly into ORD. $\endgroup$
    – GdD
    May 17, 2022 at 13:11
  • $\begingroup$ Today I learned that lead has not yet been phased out of aviation fuel. $\endgroup$
    – Michael Seifert
    May 17, 2022 at 13:23
  • $\begingroup$ @GdD The full trip has me doing everything from Class C down to abandoned gravel strips in the middle of nowhere. $\endgroup$
    – William Walker III
    May 17, 2022 at 13:36
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    $\begingroup$ It hasn't been phased out of aviation gasoline yet @MichaelSeifert, but it is being worked on. Jet fuel has never had it. $\endgroup$
    – GdD
    May 17, 2022 at 13:54
  • $\begingroup$ www.pure-gas.org $\endgroup$
    – acpilot
    May 17, 2022 at 23:05

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In theory, flight planning tools will show you where mogas is available and the price. However, a quick look at SkyVector shows only 8 airports in the entire CONUS, and none of them are along your route from MA to GA. Most likely, the places that do have it simply aren’t uploading the data.

Fortunately, some folks have created their own maps, e.g. FlyUnleaded, that paint a much more encouraging picture. It just adds an extra step to your flight planning.

In general, you’re more likely to find mogas at smaller airports that have a large light-sport and ultralight presence. Anywhere big enough to carry jet fuel is unlikely to carry mogas too, simply because they don’t want the hassle of carrying too many fuel types.

It’s not all bad news, though. 100LL is pretty much a given if an airport carries fuel at all, and your ICON can use that when needed, even if it’s not ideal.

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  • $\begingroup$ Honestly given the high-temp vapour-lock warning, for the lower half of the trail, and since the flight will be simmed for late-june/early july, I'd plan on never running with less than 50% avgas anyway until the OAT was regularly below 90F, so it's not a huge deal, but that link is pretty nifty, thank you! $\endgroup$
    – William Walker III
    May 17, 2022 at 15:17
  • $\begingroup$ If you're going to use gas from a service station, it'll have to be premium to be alcohol free, and even then you test it with the water/shake test to make sure there's no alcohol in it. I use mogas in my Lyc powered homebuilt and did have problems with incipient vapour lock during really hot weather, and finally installed a cooling shroud on my engine fuel pump which seems to have fixed the problem. $\endgroup$
    – John K
    May 17, 2022 at 16:22
  • $\begingroup$ @JohnK Since ethanol boosts octane, premium may have more than lower grades. It’s unwise to use gas from any auto filling station in a plane unless you can verify yourself that it’s truly ethanol-free. $\endgroup$
    – StephenS
    May 17, 2022 at 18:53
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    $\begingroup$ @JohnK The POH for the A5 specifically says automotive grade mogas with no more than 10% ethanol is a-okay, and lists it as the first fuel option, no less. $\endgroup$
    – William Walker III
    May 17, 2022 at 20:09
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    $\begingroup$ @ William Walker III you're good to go then. Just make sure you use a quality brand from a station that sells lots, and that the fuel is summer grade (lower vapor pressure). The lead is also incompatible with synthetic oil, so if the engine is using automotive oil don't use a full poly-alfa-olefin synthetic if running avgas for extended periods. PAO synthetics are not able to hold lead combustion products in suspension,as Mobil discovered after a few years of selling AV1 and a big class action suit. I believe that Aeroshell Oil Sport Plus is a semi-synthetic and is ok with leaded avgas. $\endgroup$
    – John K
    May 17, 2022 at 22:26

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