kryptonjohn:
It's confusing. I would have though modern cars would be able to detect knocking and retard the timing to deal with it. However... does that make the combustion less efficient?
Also, I have been told that the cost of producing high octane petrol is no way near so much more expensive than the pump price differential... which is there largely for marketing reasons. If so, and if higher octane can be more efficient, then that sounds like marketing considerations are increasing pollution?
Bye bye efficiency and power.. A lot of modern cars do have knock sensors. In my BMW it does have a knock sensor but it just throws a light if it starts to knock. Has not cut power on me when I did that silly fuel up.