I have to step in and make some corrections here, some of you are off-base.

Pinging/detonation is when there is more than one ignition within the combustion chamber, and the flames crash into eachother. That forceful crash causes the sound you hear (the rattle). It hammers pistons and will basically destroy them. It has nothing to do with valvetrain and it won't cause valvetrain problems in the rockers or further back, just the valve faces themselves. It happens when the combustion chamber temperature is high enough that it can ignite fuel without a sparkplug fire. It's usually from a sparkplug fire - and another ignition in a different area - that crash.

The different octane ratings have different flashpoints for the fuel.

93 octane requires a little more heat to ignite than 87. If there is no rattle, there is no pinging/detonation and there is no damage. It's either happening or it's not. When you hear it you know it and can identify it. Others brought up pinging/detonation happening when you can't hear it. It can happen on a minor level to where you can't hardly hear it - but that means it's BARELY causing two flames to crash into eachother and therefore is not damaging. This would be as if it were on the verge of full blown pinging/detonation. If you can't hear the rattle then flames arn't really crashing. If you want to get technical, there is some minor pinging/detonation but that is when it's on the verge of actually pinging/detonating. That rattle - is the ping/detonation so if you can't hear it than it's not really pinging/detonating.


It's not the mixture lighting off before the spark. It's not pre-detonating - its called detonation. There is nothing "pre" about it.

Yes, a reason to use higher octane is to avoid detonation. It has nothing to do with the valve position.