could be hard to say what the final rating would be.
Curious info stated in the bottom article about mixing unleaded with leaded.
http://www.nsxprime.com/FAQ/Miscella...lAdditives.htm
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Blending a leaded fuel with unleaded, however, pushes the octane up a bit more than the math would suggest, due to the effect of the lead. Just a gram or two of lead blended into the unleaded fuel will raise the octane number significantly. Commercial leaded racing fuels contain anywhere from a trace to six grams of lead per gallon. If you were to mix 50 percent 110 octane leaded fuel with 100 octane unleaded, you would actually end up with an octane number around 106 to 107. Keep in mind that even the smallest amount of lead or leaded gas line with unleaded, could spell the end of your catalytic converter or oxygen sensor. The same holds true for using octane boosters intended for off-road use only. A word to the wise, check for any lead content in all the additives you might mix with your unleaded gasoline. And check with your state emissions regulations for street use.
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also Vizard thoughts
http://www.youtube.com/watch?v=CWwCtT_CwYQ#t=10m41s