Originally posted by SPIKES
when you fill up again after you have run regular with premium .. how does the computer detect this and advance the system??
Pretty simple. The computer advances ignition timing until it " hears " knock.
Then it retards the timing in small increments until knock is gone.
I.e., you cheap out on octane rating, you will end up with less timing advance & slightly less torque/hp/snap, balls, whatever you want to call it.
The difference would be hard to notice for some people.