Tronman, 100LL is aviation fuel. It's not legal for street use. It has lower volatility and may result in hard starting in a car. It's designed for engines operating at high altitude, i.e. piston engine airplanes.
The octane rating for Avgas is derived using a different formula than automobile gasoline.
The 100 rating is based on the Motors Octane Number (MON), whereas automobile gasoline uses the AKI rating, which is an average of MON + RON (Research Octane NUMBER).
That works out to an AKI octane rating for 100LL of about 108.
100LL is also known as 100/130 octane. The 100 is the octane rating based on lean mixture conditions for cruising and 130 octane at rich mixture conditions at full power.
