There was a comparative test in the German magazine Auto Motor & Sport some years ago with various identical vehicles (mostly BMW and Mercedes) using  95RON or 98RON. They were comparing loss of power from the use of 95RON.

In the case of some models the difference in output was very small but in various BMWs the HP difference was as much as 8-10%! I presume high output engines like Porsche lose a lot too.


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"Form follows function"