[pdxmotorhead]

Ideal Octane rating is a function of Engine tuning, Compression ratio and outside air status.

Oregon winter with 50%+ humidity and < 65 degrees = 87 OCtane.
Oregon Summer with average humidity and 60 to 75 degree air= 89 octane.
Oregon summer with < 40% RH and > 80 Degrees = 92 Octane.

If your running fuel with more ethanol you can drop a level in octane because standard octane ratings don't account for the alchohol content correctly.

For instance, Sunoco GT+ 104 octane (With ethanol)will dyno higher than 110 Octane Leaded Sunoco if air temp is over 75 degrees. and as a bunus will drop cylinder head temps about 30 degrees. But their 104 octane unleaded is less power than either fuel across the temperature range.

Highest HP is JUST below the knock threshold.

Dave