This comes straight from Brock Davidson, one of the world's premier bike tuner and drag racer:
The best and most powerful gas for the street is Shell 89.
I then contacted them for clarification.
Here's their reply:
Using a higher octane than necessary will hurt performance. That is why we use lower octane, most stock motor bikes do not need to run 91 or whatever the manufacturer recommends. In stock motor 99-07 Suzuki Hayabusas we use 87 octane, they are lower compression than the newer bikes. Most of the newer bikes are little higher compression from the factory so we use 89 octane. We have had better performance results and no issues with detonation, and we save money at the pump. As for your Ducatis, we do not do a whole lot with the Ducatis. It would be up to you whether you try a lower octane or not. If it were my bike, I would throw some 89 in there and see how it does, if there is any “pinging or knocking” I would switch back to the higher octane. But that is a choice that you will have to make yourself. Also, keep in mind all this is assuming we are talking about stock motor bikes with NO power adders such as nitrous, turbo, supercharger, things like that. I hope this clears things up a bit. Let me know if you have any other questions.
Steve Syx
Brock's Performance
Sales Manager
I've been using Shell 89 in both bikes all year with no issues.
Truth be told, my happy butt dyno probably couldn't tell the difference with 91 anyways. YMMV.