100 Ll Avgas

[Rodger]

We in Calif. have only 91 octane as a maximum choice at the pump. Has anyone had any experience with 100 LL avgas?
Pros, cons, thoughts.

[Richard Hudgins]

Rodger,

You may wish to look at these sites. Some fairly good information on Avgas.



Avgas

Avgas2

There are major differences in Avgas and autogas. Vapor pressures, specific gravity, etc.

If it were my car I would go to the race fuel folks and mix if I was having a problem with detonation based on low octane ratings.

I share your problem. My 928 does not like the current offerings in California. The engine management system is constantly backing off the timing and going rich to avoid detonation. It loses in the area of 75 hp. with the current available fuel over 25% race fuel/ 91 Shell mixture.

(This on a chassis dyno.)

[maxrpm]

I was told that avgas should be avoided because among the other reasons listed in that nice link(thanks Richard) there are additives to keep the fuel from freezing at high altitudes. A friend swore by avgas until the back of his pristine black GTO became discolored. We asked engine builder and aviation enthusiast Lee Bandrow and he quickly knew what it was. He scolded us like disobedient puppys and sent us on our way.

[Mark IV]

...AVGAS is not legal to put in cars! No road tax collected or paid!

But don't let that stop you.....

Rick

[RPRICE]

You know everyone has a story, but a knowledgable engine builder and plane owner in Birmingham told me that 100ll actually burns slower than car gas. His recomendation was to mix at 20%avgas with 80% 93 pump gas to increase octane rating. But at that rate it would not slow the fuel burn down any. As I said, it's all Greek to me, just reporting what a self proclaimed expert said.
Richard
Memphis