I'm sorry I missed your response with year and model.
Your car has a knock sensor and will indeed prevent preignition if everything is working correctly which it most likely is. Running lower octane fuel will not hurt anything, but the savings will be small.
If you stay with premium, there is a resistor in a wiring harness near the master cylinder that you can remove that will increase the maximum ignition advance by 6 degrees. It will help take advantage of the premium fuel.
There was a thread about six months ago with many pictures of this resistor and its locations among different models. This resistor is in the circuit where the dial in one of the above posts is installed in Euro cars. The dial on the Euro cars simply changes the resistance in this circuit to compensate for fuel grade.