yeah, octane is higher in Europe, and gas is more expensive too.
After reading the link (thnx 4 the link), I learned that higher compression engines require higher octane rating. Octane # means the compression it can handle before self-igniting

 

I don't understand whya 87 enginewould spend more gas using 93... though it would be a waste of $$$, it wouldn't be of gas... its =...

 

The octane number is a ratio of iso-octane to heptane to perform the necessary anti-knocking capacity.

 

yeah, but anti-knock means that it would not detonate before it's supposed to, due to the fact that the gas can't handle higher compressions.

 

Speed of the flame-front issorta indirectly related to anti-knock-index, but slower flame-front = less pressure in cylinder.

 

Octane LABELING is higher in Europe. Europe posts RON on the pumps, which is a higher number for the same gasoline. And Im surprised the M3 didnt have a knock sensor.

 

Just keep putting in the 87 and everything will be okay!