[GregK]

I have using regular since the car was purchased. I may try a tank of premium just to see if there is any perceptible difference in performance....

 

[GregK]

The engine is most efficient right >< at the ragged edge of pinging events. The only way for the computer to determine this is to vary mixture/ignition timing real time as conditions change until ping is detected and then back off (adjust the mixture/timing). That is happening constantly no matter what fuel/octane you're running.

So David what are you running in your S60???

 

[GregK]

It's probably my imagination, but after one tank of premium there seems to be less hesitation upon acceleration! I'm going to keep with the premium for now....

 

[GregK]

FWIW......a Volvo mechanic in our car club recommends using premium for nothing more than the additives that are part of the mixture.....