Water/Avgas/Gasahol/Mogas

Jim -

Yes, you can remove alcohol from a gasahol mixture, but in so doing
you will have a remaining all-hydrocarbon fuel that has substantially
less antiknock capability - lower octane. I don't know how much the
octane reduction is but I suspect what you have left would be marginal
even in a lawnmower.

But to separate the mixture, simply mix the gasahol aggressively for
several minutes with a substantial volume of water, then allow the mix
to settle. This will allow the water to remove most of the alcohol
from the mixture so that only the hydrocarbon component is left. The
water at the bottom will now have the alcohol in solution.

Yes, gasahol has eliminated gas line freezeup problems. But no way
would I want to put it in an aircraft.

You can test for alcohol in a fuel sample by mixing about 10 parts
sample with 1 part of water, shaking the mixture for a minute, let it
settle, and see if the apparent volume of the water has increased. If
it has, you had alcohol in the original sample.

I check each car-filling-station load of fuel I buy in Wisconsin,
where gasahol is not mandated. The station dealer is aware of our
aircraft use, but of course he is somewhat in the dark with the
regulatory climate so we can't really depend on him. Otherwise I try
to buy fuel from an FBO that supposedly has a certified load of Mogas.
A few filling stations in Minnesota, where gasahol is otherwise
mandated, and marinas will have a pump of straight gasoline for "old
engines" etc on the side somewhere.

Gasahol can work in a processor controlled car engine that has a
closed loop system to control spark timing and mixture. An engine
properly operating on gasahol will only produce about 95% of the power
output of a hydrocarbon fueled engine. Non processor controlled car
engines just run a little feebler, although the powers that be say
they will emit less bad stuff. There is controversy on this.

Airplane engines have no processor, and even if they did, giving up
another 5% of the takeoff power would be out of the question for a
certificated aircraft. Maybe with a reduction in allowable gross
weight? But what about the reduction in octane? Still lower
compression? Ugh! It doesn't make for a good solution.

At any rate, aircraft fuel systems have not been made tolerant of
alcohol laced fuels probably because there are so many other technical
and legal obstacles to their successful use.