I'm no automotive expert but with the common rail technology now available, I believe there are diesel powered series now and I suppose long term it might not be as barmy as it sounds :think:
I've heard that the change will result in a 60% reduction in "harmful" emissions and a 20% increase in fuel efficiency of the engines as some of the more advanced computer-controlled carburetion and engine management systems that have been developed for unleaded engines can be introduced. It's also going to save the teams money as the new unleaded racing blend will be cheaper and they will be able to use more "off-the-shelf" technology from the automotive industry. However, don't expect to see them using 85 octane. Sunoco Fuels is calling the new blend "260GTX," and according to their webside has an Antiknock rating of 98 and a Motor Octane of 94.
Some more info on Sunoco's line of Unleaded Racing Fuels -