US gas stations have 2 octanes, or grades, of gasoline: 87 and 91. To get the 89, they mix the two. Usually only the 91 has the new cleaners in it, but some brands (QT, for one) put it in all their grades.
A note about trying to "de-carborize" your engine: some guys have used water, or spray carb cleaner, running it through their motor while reving it up. While this will usually clean the carbon off the back side of intake or exhaust valves, there is a decided risk of getting some of that carbon stamped onto the valve seat, thereby possibly causing a valve to burn. Be careful if you try this!
