Re: AvGas Screaming

[Mitch Loescher <Loescher@tamu.edu>]

At 01:07 AM 4/28/96 -0500, you wrote:
>> >My favorite airfield is 82c for 110/105 avgas which aint so bad.
>> 
>> ONCE AGAIN..... AVGAS does NOT Have the lubricants that the auto pump gas 
>> does have that is IMPERATIVE for the fuel pump to last more that 15,000 
>> miles......
>
>Is it possible to add lubi's like you can add octane booster to boost 
>octane? By the way, does that octane bosoter really work?

Ok, can anyone on the list give any specifics about how and what lubricants
oil companies add to car motor gasoline? 

I was a contact engineer for Exxon for a while and knew the mogas blending
contact well. To my and his knowledge, no lubricants were added to mogas
just for FI cars.  For that matter, there are alot of FI airplanes these
days and they don't add anything special, although they do vapor lock badly.
Lots of additives are used for solvent purposes (miracle FI cleaners), and
streams are admixed for octane such as MTBE and reformate (aromatic blend)
and C4,C5 for RVP control.  Actually they take great pains (and spend big $)
to insure that high MW HC's (like the stuff that would be good lubricants)
are kept out of gas because they burn poorly and would send unburnt HC
numbers through the roof.  Gasoline has hydrocarbons from C4 to about C12.
Lubricating HC's start above C20.  

About avgas... The base blendstock for avgas comes from different places in
the refinery.  Principally this is for higher heat of combustion (good) and
lower density (good).  Car gas has a density of about 6.17 lb/gal.  Avgas is
about 5.9 lb/gal.  They also use alot of polymerization (C3=oligomer) and
alkylation (C4= oligomer) blends for mogas because they burn well and are
basically synthetic fuels (as opposed to virgin naptha based blendstocks).
Alot of avgas's still have TEL (tetra ethyl lead) which is a nono for any
car's cat, O2 sensor, and is also bad for plugs.  Even the 100LL (low lead)
has TONS of lead compared to mogas.  You see, in 1972 (? may be off a year
or 2 here), when the EPA was first getting its muscle, an agreement was
reached between EPA and FAA about environmental control of aviation and
airports.  The FAA has control of environmental issues on airports and on
airplanes for safety.  So EP issues like lead, evaporative emissions etc.
are handled by the FAA.  That's why every winter, zillions of gallons of
glycols (all toxic) are sprayed (at high temperature) all over planes to
deice them, which usually then wind up in the airport's storm sewers, but if
you and I do that, we'd be breaking the law.  Evap emissions aren't a big
deal though.  About twice the amount of gas is released to the air every
year in filling stations (spillage and vapor displacement) than is sold for
piston avgas.

The octane boosters out there use MMT (methylcyclopentadienyl manganese
tricarbonyl or a similar derivitave) to boost octane using similar chemistry
to TEL, only with an Mn organometalic not lead.  Of course, you'll still
have manganous oxide (a solid) exiting through the cat and exhaust.  They
say it's ok, but I'm still nervous.  Before you buy racing fuel you should
see how they get the octane.  If it's by tons of MMT in an avgas blendstock,
I'd be worried.  I think Phillips makes a racing fuel.  I could be wrong,
but last time I looked only one major oil company made racing fuels.  I'd
stick with that rather than Joe Blow's fuels since you never know what Joe
is blending in that garage.

BTW, TEL (like most heavy-metal organometallics) is highly toxic, like drops
on your skin = cancer toxic, so if you find a way to get some to try
blending your own, I'd think twice about it.

 - Mitch Loescher