[annoyingmouse]

No reason you should feel any difference. Your engine doesn't tune itself to the fuel you buy, it doesn't know. It runs normal until a problem such as knock\detonation occurs then detunes itself as much as needed to run safely. If your car is going to knock on any type of fuel, it will probably happen around peak power, the top of your RPM range which most of us don't use much in daily driving. Knock is not guaranteed to happen with low octane fuel, nor is it guaranteed not to happen with high octane fuel.