If you do get detonation and you are happy with a little less power, you can change the resistor that is located near the master cylinder to allow for burning lower octane fuel.

The euro cars have a dial that selects a different resistor to adjust for different fuel grades. US cars have a fixed resistance there. If you pull out the resistor it gives max advance and max power, but you have to burn premium fuel. By putting in resistance you can retard timing and allow cheap fuel to be used without detonation.

That said, remember that if you do that so you can run cheap fuel, that fuel will not take you as far down the road as advanced timing and premium fuel.

Good luck,