Wow, this thread got carried away while I wasn't looking
. I hope I have a chance to add my $0.02...some of it fact and some of it opinion and I'll differentiate the two.
Knock happens first, which the Knock Sensors hear to which the PCM responds by retarding the timing.
This is a bad thing because knock happens first and then the timing is 'corrected'. Using Knock Sensors is a reative method to deal with a destructive problem, using higher octane fuel where required is a proactive method the dealing with knock.
The PCM can only retard timing by 15 degrees maximum.
Part throttle conditions can sometimes have ignition advance settings of 35 degrees, can the PCM pull sufficient timing to eleviate any knock?
The Series II L67 hypereutectic pistons are not strong. (Not sure about the Series I).
Under normal operating conditions the pistons are fine. When subjected to very high heat from lean conditions or extra load from pre-ignition or detonation, the weakness in the piston around the dish near the upper ring land is subject to fail. The upper ring land is very high up on the piston for emissions purposes but is a weak point from a high performance perspective.
I would expect that either coating the top of the piston with ceramic would help and that forged pistons would take more 'abuse' than stock pistons.
For my money I would rather not be behind the 8 ball and rely on the knock sensors and PCM as my only means of dealing with knock. I would be proactive in using higher octane fuel and working to eliminate causes of knock before they happen.
Of course the other side of the coin is for engines that do not require higher octane fuels should not use them. When an engine is designed for 87 octane fuel, it likely does not have the capability to use extra ignition timing advance to take advantage of the fuel. In that case, higher octane fuel will burn slower and contribute to carbon build up and high emissions.