SW, I'm sure you're right about that but I'm just saying vehicles using lower octane than they were designed to run on are likely to "ping"...I'm not saying every single vehicle will ping on 87 octane but it's not uncommon.
mikey, are you refering to vehicles made to run on premium or made to run on regular unleaded? 87 octane burns faster than 91...the ECU can only !Removed! the timing to a certain point, if it's already retarding the timing all it can but the mixture is still "pre-ignited" because of the added heat, wouldn't you get pinging because of the extreme combustion temperature?
I've seen vehicles come into the shop that fail for NOx, they've been running 87 octane in vehicles made to run on 91 octane. I'll tell ya, those vehicles usually ping under acceleration.