It is my understanding that this why alcohol and straight pump gas has never been endorsed by the FAA: alcohol absorbs water. Water in fuel creates a nightmare of problems from freezing at altitude to low power, etc That is why MOGAS at airports has the same rating in octane but is refined differently.
Personally, everything I read leads me to draw the conclusion that the engine of the future in GA aviation will be run on JET A, kerosene. They already have several diesels that run successfully on it, and it is just a matter of time before they eclipse the gas engine with popularity. The slower burning and power making diesel also work wells with props. A light weight version would be perfect for the KR2, Zenair, Vision crowds. But what do I know. I am just a southern mechanic from Georgia Colin Rainey N96TA
