I don’t know about ruining engines, but I do know that you couldn’t run gasohol in carburerated engine in the summer time. If you shut the engine off for 5-10 minutes on a hot day you couldn’t start the engine when you got back in the car. We used to put a cold drink cup over the throat of the carburetor to cool it down to get the car started.
Vapor lock. I remember this in the ‘55 Chevy. Modern gasoline has a summer/winter change in RVP to prevent this and reduce emissions.