Just out of curiosity how would you calculate the octane requirement of an engine you build then? I get that Scr and Dcr are just measurements but you have to start with something.
1. There is absolutely ZERO reason to run less than 91 octane (or whatever the highest octane available in your area) ever. Low and mid grade fuels have far more fillers and junk in them than premium grade fuels do, and the regulations are much tighter for premium grade fuels.
Proclaiming one can run their stuff on 87 octane is a fools errand. The money you save is pissed away in less fuel efficiency and dirty combustion.
2. Most guys can run way more compression on pump gas than they think they can. You have to control some things but it’s not hard to do once you clear your mind of all the bullshit that gets pumped out in the media and on forums.
I have been running higher than orthodox compression ratios on pump gas since the mid 1980’s. It‘s crazy to piss away power and driveability from fear of detonation.