When I lived in Colorado they switched to a 10% to 15% Ethanol mix on their gasoline. It was to help reduce pollution but a lot of it was political as the then Govenor had promised a lot of the corn growing farmers that he would push it through to help their plight.
The only thing I can recall is that a lot of older cars with the diaphram type fuel pumps soon blew out the diaphram, once replaced they seemed to be fine. I believe due to newer materials being used in the replacement fuel pumps. Some people complained about vapor lock on very hot days but that used to happen anyway. We lived at 6,200 feet elevation so we had a 20% drop in horse power to start with and on a hot day we did get some vapor locking.
Dennis