The Axis in Europe had to make do with 87 octane gas for aircraft. The US produced 100 octane aircraft gas and shared it with the British; both got the extra performance from it. The DB601/605 engines would've been designed even better if aviation gas was available to the Germans.
I don't knw what the Russians used. My guess is lower grade.
Here's an article on 100 octane gas. Developed by a Frenchman but used by the US. It says the Germans had 89 octane gas and the Japanese 87 octane fuel.
https://sofrep.com/news/filler-up-how-high-octane-gasoline-saved-untold-allied-pilots-during-wwii/
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