Where do you come up with this? Mistimed ignition? The worst thing that can be done to an engine is detonation. This event will eventually destroy a piston. This is not something we have to worry about in our stock engines running 87. If we run high compression heads or advance the timing then we may need to use a slower buring fuel(higher octane) to prevent detonation and engine damage from occuring.

Running 93 in a stock engine designed for 87 is not going to cause "mistimed ignition" and in no way will cause damage to an engine. Not that there is any point to running it though. Do some google searches on Detonation for more information.