Thats the consensus that I have heard. The LX guys have more info on this. There may be some "Tune" that allows 89 octane, but to understand why, you need to understand what the "tune" does: The factory preset fuel and spark curves are modified and altered. The spark advance may come in sooner (In rpms) and have much more advance than stock. Just with our old style cars, too much spark advance equals detonation. 100 octane fuel can cure that, right? The "tune" can add more duration to the fuel injectors which will help quell SOME of the detonation, but it can only go so far. It all comes down to the octane of the fuel.