The octane rating has nothing to do with how clean the combustion is.
The additive package is designed to adjust the octane rating for those engines that need it .
The PCM and hardware setup on ''these' engines (not some other make), measure the rotation time of each cylinder as a way to monitor missfire and general power contributuoin to the overall power of the engine.
It is this area where the engine becomes sensitive to rotation time that a more conventional engine design will not be.
Running an octane that slows combustion time will affect the rotation time and result in no long term benifit.
You can't get around the software and the hardware design just changing octane of the fuel.
Stay with 87 unless there are pinging problems not due to malfunction or fault.
Or use a tuner capable of advancing the software timing to take advantage of the slower combustion time so the 'peak' cylinder pressures occurr at the same point after top dead center as with stock timing and 87 octane..

i notice a diff when i goto shell and put v power in my tank... my truck seems more responsive and a few extra mpg... may not make sense from what the responses are to this post. just throwing in my 2 cents