this is the anwser i got on the us forum on my Q about on what fuel(ron) are
US sti made to run

"Pretty sure the minimum recommended US fuel rating is 91... but as I mentioned above, US octane ratings are given as the average between Research Octane Number (RON) and Motor Octane Number (MON).

Research is the "theoretical" octane equivalence and Motor is the actual observed octane equivalence in a laboratory motor. MON is always a good bit lower than RON.

Above I said 95RON is probably equivalent to US grade of 93.

So with our minimum recommended 91 US grade fuel, that would be maybe something like 93RON for european grading."

i think US STI are better if they can run on 93 RON a still have great performance

 

wouldnt it be nice to have a sti with 300hp and it runs on 93/95 ron