To those who fly with STCs for motor fuel instead of avgas, is the
phase-out of MTBE affecting you? The federal government hasn't banned
MTBE outright (some individual states have) but will not protect oil
companies from MTBE lawsuits so MTBE is being phased out by next week in
most places. MTBE isn't the issue here, but ethanol is. Ethanol will
be replacing MTBE as an oxygenate and is also being promoted as a
(heavily subsidized) renewable energy mixed with gasoline. MTBE is
under political attack because it has been found in ground water where
gasoline has leaked from tanks.

(Apparently gasoline, benzene, toluene, naphthalene, ethanol, and other
pump gasoline ingredients don't bother people as much when they leak
from the same gasoline tanks, but that is understandable since the human
body can smell or taste MTBE in fare more quantities in drinking water
than these other carcinogenic contaminants.)

Many or most aircraft mogas STCs prohibit gasoline containing ethanol
due to its tendency to attack certain seals, gaskets, and parts in
aircraft fuel tanks, fuel systems, and engines. So for those of you who
use motor fuel in airplanes, is the lack of motor gasoline that doesn't
contain ethanol becoming a problem?

By the way ethanol contains less energy per gallon than gasoline. Enjoy!