High compression engines are designed for high-octane fuel. In the FWD Volvos, the knock sensor inhibits engine performance as to prevent burned valves and the like. Preignition, regardless of what the source you cited says, is bad for the engine: it's casued by fuel igniting outside the combustion chamber....death to your valve stems.

In Europe this summer, I noticed the 'regular' grade of fuel is the same as US 93 octane (super in most states).

There is a useful post HERE.

for a ton of info, do a google search on "flame front" octane



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David
1998 S70 T5SE // misc mods (mostly lighting) // red calipers
1992 940 GLE // Hella Micro DE foglights and 170K