Kayak Chris wrote:
> but on a trip, how is one supposed to get autofuel? don't a lot of
> airports require you to buy their gas? (I got caught up in that once).
I've found that mogas at airports is typically 87 octane or so....not
usually good enough for a high compression engine, especially those with
poor combustion chamber design (on VWs and Corvairs this comes in the
form of large quench volumes). Most of the online flight planning
programs will show fuel prices and even which airports have mogas also.
Some flight planners (Airnav, for example) will plan your trip around
which stations have mogas, and even space your fuel stops accordingly.
The vast majority of my flying is relatively local, so I take off full
of 93 octane autofuel, and usually don't have to fill up again until I'm
back home. I get it from the local Raceway station, which keeps their
tanks scrupulously clean, and well-filtered at the pump. I've never
found any kind of trash in the fuel system of either airplane. I have
about eight 6-gallon plastic fuel cans that I carry it around in. It's
more convenient than going to the airport fuel pump, especially if
there's some guy there filling his Cessna when I need fuel.
Beware of "cheap gas stations" with ethanol-free fuel. I bought some
from a local no-name establishment that had a fowl odor to it, but
didn't attribute it to the fuel at the time I was filling cans, but as I
poured it into the Swfit (which has an autofuel STC), I could smell it
again. Within two weeks, the stuff had "blown up" the 1.25" fuel lines
connecting the wing tanks to the sump, and all the fuel had drained out
onto the hangar floor. Thankfully, I'd never started the engine, so
those hoses were the only damage. Autofuel can be a crapshoot. I only
buy it from a reputable station, and Raceway near my house is a place I
trust. They only sell 93 octane with ethanol, and that's what I burn.
My fuel tank is vinylester, so it can take it. Most epoxies cannot take
Autofuel is more susceptible to vapor lock, which can ruin your day in a
hurry, and it usually happens on takeoff. Proper cooling of the fuel
line can mitigate this. N56ML uses a fuel recirculation system and
blast cooling of the Ellison's pressure regulator to keep the fuel from
To its credit, 100LL is normally scrupulously tested at airports, well
filtered, and turnover is pretty good, whereas mogas at airports tends
to sit longer and go "stale" faster due to impurities. Vapor lock
isn't as big an issue with 100LL either. There's a lot to be said for
100LL, but you have to manage the lead buildup, as discussed previously.
In N891JF (the VW powered KR2) I normally run a 50/50 mix of 100LL and
93 octane with ethanol, with less autofuel in the summer and more in the
winter (out of vapor lock and detonation concerns).
100LL is the safe way....
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