Is that 100 octane using the RM/2, Research, or Motor method. According to my calculations, my 65 Riviera whilch requires either 99 research or 90 motor method, would require 94.25 RM/2 method octane.
If I use the 90 RM/2 method octane (non etthanol) and use 2 bottles of Gumout octane booster, I should end up with 93.5 octane. Close enough.