[masraum]

Originally Posted by JackDidley

I have not used additives in a long time. I did recently do a test on gasoline. There is a difference. At the dragstrip I was getting knock retard on 93 octane from Sams. I added 5 gallons on 110 race gas to 5 gallons of Sams 93 and got zero knocks. I did this to be sure I had no mechanical issues. I tried 93 from Caseys and also got knock retard. Finally tried 93 from Sunoco and got almost no knock retard. So, when I race I will use Sunoco 93.

Interesting. How do you know you were getting knock? I assume something running an aftermarket ECU?

You've also got to be careful about the specific station. I used to live down the road from a Chevron station and almost always got my gas at that station (in a different car from the Porsche). I had noticed pinging in our cars from time to time. I had to get gas at another station besides my usual Chevron because I didn't have enough gas to get back there. I got gas at one of the non-major brands that you'd expect to have cheap gas and additives. I filled up from that non-name brand station and the pinging immediately stopped (the car had been nearly empty). I completely stopped using that Chevron and never had pinging again. I don't know if they just had crap tanks that leaked or if they were "topping off" their tanks with water or what.