hi
The octane count may be 93, 87 or whatever, but as it sits, it diminishes.
also being that the higher grades of gas cost more, they sit in the storage tank longer than the cheaper grades so you actually run a risk of getting bad gas, thinking you're getting something better. I'm guessing condensation is occurring.
If you've ever seen them replace storage tanks for the gas at the station, you should see what I'm talking about
Let's also not forget that some store owners like to cut corners on things.
I've seen a tanker put gas in the pumps at one place, he put the SAME gas in all three storage tanks without switching compartments from his truck.
That place is no longer in business, but it's still happening elsewhere.
I get a kick out of ppl trying to tell me that gas from one brand is better than the next.... the "off brand" gas from the other guys is pretty much the same gasoline, they just bought it wholesale.