Avgas contains 5X the amount of lead as leaded automotive fuel. The lead is the reason for the 100 octane rating. It's designed for cold weather, high altitude, and requires a lean mixture to burn efficiently. It also has a lower BTU rating than regular auto fuel- which is the heart of our power source.
The engines it was designed for almost all run at a fixed ignition advance setting of either 20 or 25 degrees BTDC. Also, the engines it was designed for run at very low compression ratios in the range of 6.5:1 up to 8:1. Since the engines are air cooled, run at a consistent cruise RPM, air inlet temps are mostly freezing, the atmospheric pressure is low, and a few other odd working conditions, they came up with this fuel grade. The engine and fuel designers all have built in quite a few detonation preventatives with low BTU/high octane being one of them.
Anyways, knowing that I ran it in my track car a few times and noticed the my 1/4 mile times got slower. I rejetted the carb for an unusually lean mixture which made the car hard to drive without stalling when letting the clutch out. With the very lean mixture my 1/4 mile times got better, even better than pump gas, but not easy to drive on the street.