I've run 93 octane Shell premium on all of my vehicles since ownership...no fuel related issues as far as I can tell. When I do travel further north, 91 octane is the highest available and I use that.

And octane is a measure of "flash point", not energy content or anything else. Translated, it takes a higher temperature to ignite the atomized fuel in the combustion chamber. That means, it won't "pre-ignite" in the compression cycle or "knock" as what it is normally referred to.

This is why turbo gas engines require premium.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car