I've read on this forum (many times) that most people recommend using premium fuel and going to 40:1 mix (or leaner).
My Hobbit loves 25:1 and 87 octane. With the 25:1 mix, I calculate that the octane is really 83.
Anyway, I wonder how many of you properly adjust your timing to account for the increase in octane.
For my Hobbit, I tried a 1/2 gallon with 92 octane at 40:1 mix, which is then about 90 octane. The motor ran worse (no timing changes). Then, I switched to 1/2 gallon of 87 octane at 25:1 - and the motor really woke up.
I can only attribute this to not having changed the timing to match the octane change.
Is there a rule a thumb that can be used - like for every two points, advance timing x degrees?