"G.R. Patterson III" wrote in message
...


Addison Laurent wrote:

I was under the (perhaps mistaken) understanding that mogas was measured
on a differing octane rating system, and that 93 mogas was ~100 octane
measured on the avgas system?

They use a different system, but it works the other way 'round. There is
no mogas
that comes close to 100 octane avgas. Fortunately, most engines that are
burning
100LL are actually certified for a lower octane.

According the the EAA fact sheet on autogas, you can get a good idea of
the
octane equivalent by subtracting 5 from the mogas anti-knock index (the
"octane"
rating on the pump). So 93 octane mogas would be about 88 octane on the
avgas
scale.

http://www.eaa.org/education/fuel/detonation.html


And this article as well:
http://www.avweb.com/news/columns/182132-1.html

May 27, 2001

Pelican's Perch #43:
Detonation Myths

We've all been taught about detonation in piston aircraft engines. It's what
occurs when combustion pressure and temperature get so high that the
fuel/air mixture to explodes violently instead of burning smoothly, and it
can destroy an engine in a matter of seconds. Right? Well, not exactly.
AVweb's John Deakin reviews the latest research, and demonstrates that
detonation occurs in various degrees - much like icing and turbulence - with
the milder forms not being particularly harmful. Heavy detonation is
definitely destructive, and the Pelican offers some concrete data on how to
avoid it.