theiceman

i agree with this , the knock sensors pick pinging ( preignition) up very accurately and are able to retard timing to compensate. Any decent data logger you can track ignition timing angle.

eaks

Yes this is on a tuned car. But even with my stock tune and doing the first logs with my tuner I found timing by pulled (it may have had additives in the fuel as it was approaching winter the first time I went through this). Every car is different and most likely not noticeable unless you are datalogging or using vbox or something to measure times. Again it is hard to say 100% because there are many factors (DA, weather, slopes, ect) but the logs I pulled over and over showed I had a lot less timing being pulled when using Petro 94 vs chevron 94.