AutoGas & Vapor lock
The point about "Let it sit" isn't totally accurate. Phase separation only occurs when the amount of water (from condensation) exceeds the ethanol’s ability to absorb the water. If auto gas sits too long in an aircraft tank (which may be many, many months) Carefully sumping the tank prior to flight "should" identify this issue (as what fuel is left may be a lower octane), requiring the fuel to be replaced..
So, if you keep the fuel under pressure, from the source, to the engine, vapor lock is impossible. At least that is what happens in auto's as the fuel pump is IN THE TANK. Wouldn't this (and other fuel system changes) work in airplanes? Yes, other fuel system changes include Teflon hoses (or other ethanol compliant materials), no 90* fitting to the engine, and heat shielded lines must be involved.
There are MANY in the experimental domain doing just that. I've been running 93 OCT E10 gas for years with absolutely NO issues. I have an independent fuel pressure system that turns ON my AUX pump (located in the cockpit) whenever that pressure goes below a set point plus 10 seconds of run time. As long as the fuel is under pressure, and "PUSHED" to the engine pump, vapor lock is impossible.
As far as phase separation is concerned, I've never seen it happen in my aircraft, even in the high humidity Florida environment. And the aircraft may sit for MONTHS at a time with no use.
A nice experiment might be to half fill a five gallon container with E10 gas, then start adding water until phase separation occurs. You will be surprised how much "condensation" it takes to force phase separation.... Unless you aircraft is parked outside and has leaky gas caps, you probably will never see it happen.
The IO-360 with the 8.5:1 compression requires a minimum of 91 octane. 93 octane E10 gas works just like 100LL....
Gasoline boils when the fuel gets warm. When it boils expect vapor lock.
Auto Gas does not have the standards that 100 LL has. A FI engine has more fuel lines than a carb engine. The issue of whether auto gas will be suitable or not probably depends a great deal on the installation of the engine than the engine itself.
Keep the fuel lines cool and fuel below the boiling point...which we really don't even know. Also, if we run Auto gas in one tank only and use it only in cruise flight then it may be kept cooler by the nature of the fuel moving through it. Contrast that with the idea of taking off after a long taxi at low fuel flow....fuel is not moving fast through the lines and has time to heat up....and boil....and you find out during takeoff.