The alcohol content tests the same AROUND HERE, but I don't see any benefit to running premium fuel. Actually the shelf life of premium could be less..... since they don't sell as much of it.
As I said, the only issue I recognize with today's fuel is....How long it can be stored, which appears to be about 4-6 weeks, tops. Any longer than that and I can notice a difference.
When setting the idle mixtures on carbureted engines after a complete fuel system overhaul, I can notice a difference on 1/4 turn of the mixture screw (jet) with fresh fuel. With aged fuel I can turn those mixture screws 1/2-3/4 turn and barely be able to notice a difference. That right there tells me everything I feel that I need to know. I always set idle mixtures with fresh 87% fuel that I've had in my remote tank for less than 2 weeks.