"Peter Stickney" wrote in message
...

snip
The higher engine output comes from the increased Manifold Pressure.
High Octane fuels tend to have a somewhat lower energy content than
those with lower Octane (or Performance) Ratings. (Technically, if
it's over 100 Octane, it's a Performance Number.)

No, higher octane fuel burns slower; but it contains more usable energy.