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[eTiMaGo]

Originally Posted by cleong

So we should only run the absolute minimum RON recommended and anything above is just a waste of money?

that seems to be the consensus...

I've just looked through all the ECU and ignition related stuff in the repair and technical manuals... my head's spinning now, our humble little car has some pretty advanced systems...

I was trying to find out if the ECU has any kind of learning system, that might try to advance the ignition timing until knock is detected, as this would allow it to run the maximum ignition advance regardless of the fuel used. But I find no evidence of this, but also no evidence of the contrary. From what I gather, the actual spark timing is determined by the crankshaft and camshaft position sensors, and retarded by the knock sensor when required.

What I did find out, though, is that the spark advance can be set in a range from -64 to +63.5 degrees, and the normal value when idling should be between 0 to 14 degrees.

Truthfully, the only way we can know for sure, is to have some device such as the Toyota intelligent tester used by the technicians, to monitor the actual ignition timing while driving with different tanks of fuel, such as 87, 91, 95 octane, and compare the average timing between each tank. Until then, it's really a matter of educated guesswork and subjectivity...