Be careful running 100LL in your car. The LL stands for Low Lead, but it's not actually low lead AT ALL. As a comparison, 100LL has 2 grams of lead per gallon while unleaded car gasoline has a mandated maximum of 0.1 grams of lead per gallon. All that extra lead can really gum up your valves if your car isn't designed for it.
There's a place that sells paperwork for light aircraft to use auto gas in place of 100LL. They have a great discussion of the differences between 100LL and unleaded auto gas.
http://www.autofuelstc.com/stc_specs.phtml