will the pcm reset itself when goingback to premium?

[invisiblem0nst3r]

the previoous owner ran 89 now that i have it i only run 91. will the pcm and timing readjust?

 

[Psychostang]

Using a lower octane fuel, doesn't change anything. IF the knock sensors detect the onset of detonation, then the computer backs off timing depending upon its programing. If you run 87, and there is no knock then nothing changes. Anytime the engine is running, the knock sensors are listening.