[John Beaman]

Carl and Andreas:

I was under the impression that B4 and C3, seen later in the war were the equivalent of coal oil derived fuels, equal, respectively, to the 87 and 100 octane. This happened after "pure" petrol distilled from natural oil could not be had easily. 100 was used for higher performance engines like the DB 601N and for supplements like GM 1. Later engines, at least liquid cooled ones, could be tuned to take either when one or the other was not available.