Thor77

I think that is correct about the senosor. Most modern cars have a knock sensor, and until it detects premature detonation (knock), the computer will run as much timing advance as it can up to whatever is the optimum tune that they programmed. I know that's what my 93 BMW does. Generally there is no advantage to higher octane if you do not have the compression or timing advance to exploit it, so unless you are making modifications, I'd always run the recommended octane. In a pinch you can run lower, but if you bought a Challenger, man up and pay the extra 10 cents per gallon to get the most out of it.