Ok, I’m still curious as to what everyone has to say, but after a web search, I’m not nearly the first to have thought of this. Many racers have been doing this forever to boost octane. There are various formulas for homebrew octane boosters containing xylene, toluene, and other solvents. Apparently the key is to not get too carried away and to use a lubricating agent such as Marvel mystery oil or a couple of ounces of two-cycle oil or kerosene. This supposedly will help protect rubber components and other ‘edibles’ in the fuel system. After some searching, apparently many gasolines already contain methanol, ethanol, and/or mixes of xylene, toluene, and other chemicals that are already somewhat bad for rubber and plastic components, and emission control sensors. Based on the price of xylene and the amount of octane gained, it would probably be worth doing to boost octane a little cheaper than shelling out for premium, but only slightly when you factor in the bother of mixing it. So I’ve kinda answered my own question. But I’m still interested in anyone’s viewpoint. If you’re interested, here’s the Google search:
http://www.google.com/search?q=xylene+as+octane+booster&hl=en&lr=&start=0&sa=N