A minimum of 89 octane in the USA. If you like to depress the pedal, you really need 91+ octane.

The knock sensors are very good and will detect ping long before you can hear anything. The lower octane burns sooner than higher octane, especially when combined with 10:1 compression ratio, as in the NA engines. If knock is detected, the ECU will retard timing and add additional gasoline to each cylinder to keep the engine from knocking. This results in lower MPG and fouling up plugs and O2 sensors.

Considering the normal 10 cents/gallon difference in prices for each grade, 89 octane costs $1.80 more per tank than 87 octane, and 91+ costs $3.60 more per tankful. Not a bank account buster! Besides, the higher octane fuels usually contain more cleaning agents to keep your valves clean.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.