Great paper actually but my point still stands. It’s not the fuel itself that creates more efficiency, it’s the fuel that is required to help these legacy cars achieve such efficiency.

Thus, these vehicles realize an improvement from increased octane rating in accordance with their ability to spark advance to take advantage of a fuel with a higher octane rating.

It’s the engine tuning not the fuel. If you just take higher octane fuel and put it into a legacy engine you’ll have no difference in your efficiency. The ECU must be programmed, if capable.