cjman-It's hard to know what will happen. As miles go by, carbon deposits build in the cylinder. They can be the source of hotspots which can contribute to detonation. So it's at least possible that the car is more prone to detonation now than it was before you switched to 93 octane fuel. If it's not detonating with 93, I'd step down to the in-between grade (91, 89 - it varies across the country), and try that. If all's well, then step down to 87 and see what happens. This is the worst time of the year for detonation because ambient temps are the highest - and the higher the intake air temp, the more possible detonation becomes. But if you haven't modded it since you started running 93, ease the octane down and see what happens. You can always go back to 93 or cut the timing back if it causes problems.