Subject: Re: Mogas -Info needed for decision making
Date: Mon, 23 Apr 2001 21:49:07 +0200
From: "Toos en Pieter van der Voort" 
Lasse,

Worked for an oil company many years within product quality and I can inform
you that the  compositional difference between
Avgas 100LL and mogas high octane is at the level of more/less of the same
components. Both products use in fact the same kind of blendstocks.
These are cuts from crude in in rough boiling range 30 - 180 C. So
bottomline mainly the mix ratio's are different and it depends also on
refinery configuration
and availability of blendstocks how an oilcompany formulates.
An important compositional aspect of Avgas 100 LL is that it contains a lot
of iso-alkylate that is rather sensitive for lead octane boosting, while
this component
is not regular (availablity is short) for mogas. Mogas uses aromatic
powerformates for octane boosting that might have higher octane rating as a
pure component
which makes it also favoured for leadfree mogas. Such does not mean that
iso-alkylates are not present in mogas but most times not as an identified
blendstock.
Leadfree mogas is also boosted by oxygenates (not a component for avgas as
far as I know) and butane ( wintergrade may contain 5-10% dissolved).
Butane is not a component for avgas for vapor-lock reasons but be sure that
a chemist will find all the species in both products and only the
percentages or ppm will differ. Composites might have different behavior
when exposed to the various pure chemical species of mo- and avgas but in
general avgas 100LL might be
more suspisious due to the lead content. An  idea might be to ask your local
oil company whether they discriminate elastomer/composite compatability in
between their  avgas and mogas. You may also ask the sealing compound
supplier whether he has experienced different behaviour for the two grades
Regards, Pieter van der Voort
Pulsar III s/n 98010548 under construction

I have asked my local EAA chapter permission to operate my Rotax 912 on

Mogas instead of Avgas for various reasons.

They have now come back telling that they have no experience with Mogas

and composite fuel tanks, as they see the compability of Mogas and  and the
internal surface of the tank as a potential problem.

Could as many of you who has been flying on Mogas let me have you

experience, in order for me to convince the chapter.

And for those of you having the Skydrive carburettor heating blocks:
My testflying indicates that the system will raise the blocktemperature

app. 30C above OAT.

The carb.body somewhat lower, but defenitively above freezing level.


Best regards
Lasse Lykke Espersen
OY-LLE
Now 25hours on the Hobbs

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