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181962
My bad. That was supposed to be E10 87 and 89. That post has been corrected.Where are you getting E10 97 and 99 octane fuel?
As for ping, I've had opportunity to test this, but I suppose there is lower limit to ignition retardation--your 2004 would have had knock sensors-- that would make pinging pronounced; e.g the PCM detects the knock from the knock sensor, but can't make further timing retard, and thus only highly octane fuel would solve.