Let's say you mix 1 part avgas with 3 parts mogas for use in your flying
O-300-powered demon. You have an STC for doing this, of course.

These two fuels have different specific gravities, so it is said. Do they
stratify? I don't believe they do. Anybody have a comment? I guess you
could pour samples into a glass tube and watch and see if they get it on or
avoid each other.