where to get 93 octane after a couple years of driving my NA on 91. I used it any way just for the warm fuzzy feeling, but that was before Katrina jacked prices up and it disappeared here, and now it is well over a dollar higher than it was back then. Supposedly it takes ALOT of those little bottles of additives in order to make a tank of 91 into 93. And even then you really dont know how much you really need, toluene is alot simpler and will be marginally more than buying half a shelf of those octane boosters they sell at autozone and other auto shops.