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From: doug@terak.UUCP (Doug Pardee)
Newsgroups: net.auto,net.consumers
Subject: Re: No Leaded Gas -- Now What? (aviation fuel)
Message-ID: <435@terak.UUCP>
Date: Sun, 10-Mar-85 17:52:17 EST
Article-I.D.: terak.435
Posted: Sun Mar 10 17:52:17 1985
Date-Received: Tue, 12-Mar-85 21:09:12 EST
References: <673@druxx.UUCP> <1349@hou4b.UUCP> <498@ssc-vax.UUCP>
Organization: Terak Corporation, Scottsdale, AZ, USA
Lines: 54
Xref: linus net.auto:4820 net.consumers:1385

AAARGGHHHH!   Let me set the record straight on aviation fuel --

The standard aviation fuel these days is called 100LL.  It is rated
on a different octane scale than automotive fuel, but is still higher
octane than your everyday automotive stuff.  The octane is boosted
both by lead and by aromatics.

Here's why you probably don't want to use it (most important first):
1) it costs about $2.10 per gallon;
2) you can only get it at an airport;
3) the airport people probably won't sell it to you anyway, because
   a) it might be illegal in your state, road fuel taxes not having been
      collected from aviation fuel;
   b) they have shortages and consider filling planes as top
      priority (not a big problem right now)
4) It is not made with different blends for different seasons in
   different locales, as automotive is -- the Reid Vapor Pressure
   is constant all the time, to prevent vapor lock when flying at
   20,000 feet or whatever.  That means it won't vaporize very well
   in your carburetor at 5 below zero, and starting will be a b**ch.
5) The fuel uses ethylene di-bromide instead of ethylene di-chloride, or
   is it the other way around?  I don't know why you'd care.
   
You can tune out unless you want to hear about the historical aspects
of aviation fuel...

Over the decades there have been a half-dozen different grades of
aviation fuel, but for the last quarter century only 80/87 and 100/130
were significant.  Even so, refiners & distributors disliked having
to deal with two different grades of fuel, both in (relatively) small
quantities.  So 100LL was developed, a one-size-fits-all aviation
fuel.  Over the last 15 years, virtually all aviation fuel refiners
have switched to 100LL.  The only major refiner that hasn't is
Standard of California (Chevron).

100LL doesn't work very well in engines intended for 80/87 grade fuel,
because it still contains 4 times as much lead as 80/87.  The result
is heavy lead fouling of spark plugs.  This is not nice, because these
engines are typically found only on single-engine planes, and are
4-bangers.  The loss of firing in one cylinder means a 25% power loss.
That means it's time for the pilot to find an airport nearby.

Most of those engine designs are long out of production.  The one that
wasn't, the Lycoming O-235, started being produced with new valves
which were supposed to permit using 100LL.  It didn't work.

Three years ago the FAA started approving, after model-by-model reviews,
using automotive fuel in airplanes whose engines were designed for
80/87.  This process is almost complete, with only a few models which
prefer 80/87 and cannot legally use auto gas left.  The big losers:
the O-235-L owners who get lead fouling from 100LL and can't use
either 80/87 or auto gas!
-- 
Doug Pardee -- Terak Corp. -- !{hao,ihnp4,decvax}!noao!terak!doug