You are correct, you can not hear a knock being retarded, but you can many times hear another symptom when it gets bad enough (gurgling exhaust, the engine struggling to provide power, engine sounding like it wants to stall, etc from misfires), or there is a secondary issue. Under normal operations, most (all?) regular vehicles experience knock retard even under normal driving conditions, and you never hear it. But when things become problematic, the associated noises usually are different than what this sounds like. That is what I was getting at. This noise is just strange. Like I said, sounds like a plastic bag flapping (quickly) in the wind, not a metal on metal "ping" sound and with no real loss in power, it doesn't seem like the KR is much higher than normal, but maybe it is just high enough? Again, just thinking "out loud" and not disagreeing.
As for the gas, here in Iowa they somewhat recently switched from 87 regular, 89 ethanol blend, and 91 premium to 87 regular, 87 ethanol, and 91 premium, skipping the 89 altogether. My old GTP said premium only, the 06 GT does not, but I bet that 87 is just too low and if I was a betting man, I would bet that the manual even says that 89 regular is OK. Since I can't get 89, then I guess I will have to pay the $0.70 gallon "premium" price for the premium gas. Do you think that a bottle of octane boost would be beneficial for this tank of gas?
