Originally Posted by
RatherBeFlying
Later WWII recips required high octanes that are no longer available (unless you special order a refinery batch).
With lower octanes you have to reduce manifold pressures to prevent detonation and consequently get less performance.
That said, I don't know the octane requirements for the engines on the B-17.
This is a 1943 training film for the B-17. Note the comments on octane fuel at 5 min 15 sec (91 octane) and then again at 7 min 20 sec (100 octane) reference to power settings.
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