iskwezm
10 Year Member
the only performance advantage of running 91 is that when its tuned you can add a couple more degrees of timing for a little bit more power.Its not going to burn any cleaner.i dont see anything wrong with 87 ive never had any sort of knock or detonation problem, ford recomends 87 dont they? but im not aware of any sort of advantage of running higher octane since its mechanicly sound as it is.