The newer (computer controlled) engines are very good at controlling detonation with timing retard. I don't think I've ever noticed it on a fuel injected car, or on the old "lean burn" cars. A different story on the 6 pack motor, (10.5 CR) with the headers open you can't hear it going on but I'm sure it was rattling like a hammer on an anvil once when we mixed 1/2 & 1/2 pump gas and racing 110, it blew the center out of a spark plug on a 1/4 mile pass. Around here it's hard to find anything but 87 octane without alcohol in it.