I would take that bet. I believe Octane only has to due with the flash
point of the fuel. Originally it was the ratio of heptane to octane in
the fuel. (Octane has a higher flash point). Now they also a chemicals
to help increase the flash point (and reduce emissions). I seriously
doublet the octane changes over a month.
Higher octane provides almost no power increase. It just keep high
compression engines from knocking. The 13B not being a high compression
engine it would not matter anyway.

If gas is left for extended periods of time (6 moths)it will begin to
gum up in fuel line ect but they sell stabilizers to prevent this.

Alex Madsen  



-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of echristley@nc.rr.com
Sent: Monday, May 10, 2004 6:43 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Mogas issues

I was asking someone very knowledgeable in the area
of epoxy systems about gas tank sealants for
composite tanks that can stand up to mogas.  His
response is below, and he brings up some issues that
I've never considered.  Transport will not be an
issue for me, but what do those of you who've been
flying with mogas think about the issue of smell and
loss of octane?

Could the latter be the reason that Rusty is seeing
such poor static performance?  The gas has been
sitting to long and gotten a little rusty?


> Jeffco makes a coating (tank lining system )
specific for Avgas.  It is
> used in Lancairs.   I don't know the number so
you'll have to contact them.
> Mogas stinks - literally.   You'll have an
airplane and a hanger that
> smells like a jet ski .   It makes passengers sick
real fast.  You will get
> tired of the transporting hassles too.   I've
never seen any data on
> storage stability, but I know the makers never
plan on it being around much
> longer that a few days.   If you wind up not
flying on a regular basis,
> I'll bet dollars to donuts that it looses octane
units with time - say 30
> days or so.  



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