hmm could you please provide a short explanation for the not-so-engine-savvy on why you have concluded that currently, RAF engines are running on 87 octane fuel? I didn't get it so far.
However, I agree that if that conclusion is correct, the FM should be changed to 100 octane across-the-board, since I don't believe that 87 octane was in front-line use after may 10th 1940.
Maybe the Tiger Moth used up remnants, though
