Octane ratings here were changed since our cars were new. It's now an averaged figure of RON and MON ratings. Formerly RON ratings were used. In 1970, Regular was 94, Premium was 100. Lead additive was phased out in 1971 and Regular octane dropped to 91 RON.
An engine will have a "favorite fuel" for whatever its state of tune. I had a '67 Honda 50cc cycle that would do 45mph on 87 octane unleaded, but would do 58mph on 106 racing fuel. Since it got 70+ mpg it was no big deal to spend the extra money for the racing fuel. It ran fine on either fuel, no knock, it just ran faster on high octane.
Vikki 1969 Goldenrod Yellow / black 400 convertible numbers matching
