The problem for the
ethanol alternative comes with “phase separation.”
That’s what happens when the fuel is saturated beyond
its capacity to hold water in solution. The water and
gasoline actually separate, and the gasoline floats on
top of the water. With MTBE you could simply pump
the water out from under the gasoline, or let your
filters remove the water, and burn any gasoline that
remained. With E10, ethanol blends more easily with
water than it does with gasoline. When phase
separation occurs in E10, the ethanol is pulled out of
the gas and stays with the water. This result is two
solutions, neither of which is good for engine or fuel
system. The gasoline left behind now has no
oxygenate; it shouldn’t be burned in the engine and
must be disposed of. The water left behind now
contains a high concentration of ethanol; this solution
is highly corrosive and damaging to any materials it
may be in contact with in the fuel system. The only
solution to dealing with E10 that has phase separated
is to dispose of the whole load of fuel, clean the tank,
and start fresh with a new load of E10.
...
E10’s ability to absorb water has yet another
drawback: it can absorb water directly from the
atmosphere through the vent while simply sitting in
the tank. In just 100 days at 70% humidity, E10 can
absorb enough water to phase separate. The shelf life
of E10 is only 60–90 days if left without treatment.
...
When it comes to winter storage, a boatyard should
run the tank down as low as possible at the end of the
season and treat what is left for the winter. That of
course goes against traditional thinking in terms of
condensation, but: better a small amount of water from
condensation than a tank full of bad gas.