I still don't buy the fact that the engine has spark/fuel mappings that will take advantage of 91 for a N/A 3800. To get to the bottom of this we'll simply have to ask a tuner who programs the things, thats the only way to get the answer.

How about you take a N/A Bonneville, put it on a dyno with 87, empty the tank, run it on 93 and see how it does? I'd be willing to bet the difference is nada, zilch, zero.

The stock PCM can adapt to a point. If you drive with a higher octane, KR will be reduced. You'll only notice this for the most part at WOT. I can tell you from experience how my own car reacted to octanes ranging from 91-95.5, and it was obvious. Both on the scantool, and by the seatofthepants dyno.

Didn't read the novel above, but Octane is just basically the way the gas burns. Not cleanliness. Engines can run with whatever, it just depends on their tuning at the time. You could make an l67 run with 89 if you wanted, it wouldn't be easy with a pcm but you could.

Higher octane= longer burn

Oh I'm sure the Supercharged models love high octane gas -- and I certainly would run the best I could find if I had one. My concern is that the base 3800 doesn't have the mappings it needs. We aren't talking about a Corvette PCM here This base 3800 is a engine that is used in a multitude of models, a lot of which are leased/rental vehicles for fleets.

Octane number is relative to the activation energy that a certain fuel needs to ignite compared to iso-octane. Once it ignites, it'll burn at the same rate.

Methanol has less than half the energy than gasoline. It'* average octane number is around 99.

I saw the thing about OBD 2 & 3, but do we know what OBD 1 does? (besides take over)

i'm very curious.