The turbo is also cooled via coolent, not just oil from what I read. Not sure on this engine but my Audi has a separate electric water pump that cools the turbo even after turning off the motor. I'll know after getting my 24. Should be any day now.
As an FYI, higher octane fuels don't offer more energy or better fuel economy. They simply are more resistant to spontaneous combustion due to compression (dieseling) which causes engine knock. This is the reason why many high compression engines require higher fuel grades. If the Toyota...