On 12 Mar 2016 19:59:47 GMT, notbob wrote:
On 2016-03-12, wrote:
It's not so much evaporation as oxidation - and both the oil and
gasoline will oxidize. It is much worse if moisture is present.
If you mix oil and etanol free gas, and put it in a tightly sealed
container in a cool location, it will last many months to a few years.
Mix ethanol gas with oil and put it into a vented plastic gas gan in
your garden shed in the summer, a few months is pushing things.
You jes put two completely different gasoline mixtures in two
completely different vessels/environments. One in plastic, one in ????.
One with ethanol (+stablizer?), one not. One "vented", one not. One
in "cool" location, one in ¿hot? Summer location. With all those
variables, how you settle on the problem being the ethanol is a
puzzlement. 
nb
Ethanol is MORE of a problem in an unsealed container. (ethanol is
hygroscopic - it attracts water) Gasoline in a sealed container needs
to be kept cool or it will burst (high vabour pressure)
If you want a premix to lat, you keep it in a sealed can in cool
conditions, and to be really sure you don;t use ethanol(because it
could already have absorbed significant moisture).
If you want gas to go bad really quick, you use ethanol gas, keep it
in an unsealed container, and subject it to wildly changing
temperatures.
Nowhere did I mention stabilizer/
So - the issues that will cause gasoline to go bad a
1- oxidation due to being in an open container
2- moisuture from condensation being in an open container with varying
temperature
3- ethanol in the gas attracting and absorbing moisture from the air
being in a vented container.
4- evaporation of the "light ends" from the fuel
The only one that is related to ethanol is the attracting and
absorbing water from the air..
Now comes the real fun. The amount of water the ethanol mixture can
hold in suspension varies with temperature, so when the temperature
fluctuates, and the gas cools with close to the limit of absorbed
water in the mix, the water and ethanol "phase separate" from the
gasoline, and drop out into the bottom of the tank or container.. The
water also has oxygen absorbed it it - which, along with the ethanol
(also an oxygenator) causes the fuel to oxydize, forming gum, and also
(if in a metal tank) causes corrosion in the tank or container.
If that water/ethanol drops out in the fload bowl of the carburetor,
that water and ethanol attack the brass parts of the carb - in
particular the jets, which get restricted of blocked with the
"greenies" from the oxidation of the copper that is electrolitically
stripped from the brass - making the engine difficult or impsiible to
start - and making it run poorly if and when it does start.
The lack of "light ends" in the fuel makes it harfer to light and
reduces the octane as well as many other desireable properties of the
fuel
That is on a 4 stroke engine.
On a 2 stroke another problem rears it's ugly head. The fuel mixture
runs through the crankcase to lubricate the 2 stroke engine - and when
water is drawn into the crankcase along with the oil/fuel premix (or
in place of it if the separated water/ethanol is drawn from the bottom
of the tank) the engine parts are not properly lubricated, and the
moisture causes corrosion of the engine bearings, frank, and other
internal parts. Reduced octane due to evaporative losses is worse on a
2 stroke because the addition of oil to the mix has already
significantly reduced the octane of the fuel
Ethanol free gas does not attract as much moisture, and does not drop
that moisture out of suspension in such large quantities, so is much
less likely to cause any of the above-mentioned problems - and when
stored in a sealed container will last significantly longer.
SO - the ideal storage situation is ethanol free mix in a sealed
container stored in a constant low temperature situation/
The WORST situation is ethanol gas stored in an open container under
fluctuating (and generally higher) temperature conditions.