We ran 130 Avgas in our racecars for a long time.
Compression ratios up to 14.5:1 .. Then they quit making/selling it.
We gave 100LL a try and found that we dynoed with the same power.
Had the fuel analyzed (Phillips) and were told that it had more lead content (by many times over) than did leaded automotive fuel. The vapor point of the AV fuel was a lot lower as well. While we didn't have any problem with vapor lock, some guys did. We used positive displacement eletric fuel pumps.

Gman is right. Engines (particularly their valves) love lead. The lead not only acts as a lubricant but a coolant as well. The lead helps carry far more heat away from the engine.

Problems in running a mix of leaded / un-leaded -
The lead will foul o2 sensors as well as poisoning the catalytic convertor with repeated use. o2 sensors will clean themselves (by heat) if not fed a continous diet of lead. Catalytic convertors will not fully recover and they will produce less output heat. The lower output heat will cause the secondary o2 sensor to set a code in the ECU indicating that the engine is not running efficiently. This will ultimately turn on the SES light on the dash.
The final problem is that it's actually illegal to introduce leaded fuel (except in the case of an emergency) to a vehicle driven on public roads that was designed to run un-leaded fuel.

Regards - Randy




If there's one thing I've learned in online forums its this:
Never argue with an idiot, they'll drag you down to their level and beat you with experience!