"Over time, Mogas deteriorates faster than Avgas"

Jay Honeck wrote in news:1189950184.266800.205080@
57g2000hsv.googlegroups.com:

If you leave it in your airplane, it isn't stored in a tightly closed
container, though, is it? It sure isn't in mine!

Um, well, it's as tightly closed as any vented tank can be. Even gas
station storage tanks aren't sealed tight, or they'd be unable to
expand/contract with temperature changes.


True,. I'd be no expert on the subject anyway.

I have noticed the difference and found that mogas, having sat in an
airplane for a few months, is a lot harder to get going than
equivelant
Avgas in the same airpane.

I have never noticed the slightest difference. Now, of course, I
don't let my plane sit for months, or even weeks -- but my motorcycle,
convertible, lawn mower(s), lawn blower(s) and vacuum, and snow
blower(s) ALL sit for many months, unused. No problemo starting or
running in the spring/winter.

I've noticed the opposite with mowers bikes and what not, usually after
more than six months, but they do still start (eventually) and seem to
run fine, but there must be some deterioration taking place. You only
have to let the stuff sit for a couple of years to watch it turn
completely to varnish, so surely there must be some progres made towards
that state in the interim.

Also, we have a shell petro-chemical engineer in our circle and he
tells
us that the aromatics in mogas evaporate more readily thuus causing
the
degradation in quality.

Again, a cite? ANYTHING in writing, ANYWHERE about this problem with
mogas?


I actually do have one somewhere. If I can't lay my hands on it in the
house here, I should be able to get a copy of it somewhere.

For ten years I've been hearing "my buddy the engineer told his
brother that..." -- and, after a decade (and over 9,000 gallons of
trouble-free mogas in our planes) I'm simply not buying it anymore
without SOME kind of evidence.

Up to you, I'm not trying to sell anything anyway..



IMHO, as with so many of these things, we desperately want to believe
that gasoline that costs 25% more is really better in some tangible
way. I have seen no evidence of this, at all, over a decade of use.
That would zero, zilch, nada -- no difference.

Of course, to that end, there are STILL people out there who will pay
a premium for high-octane gasoline for their cars, despite
overwhelming evidence that this is a complete waste of money. The
oil companies just shrug their shoulders, pocket the extra dough, and
keep making commercials touting how their brand "cleans your
injectors", or some other BS.


Well, octane has nothing to do with quality. In fact, any octane present
in fuel has little to do with it's octane rating. Engine octane
requiements are arrived at by feeding an engine a fuel consisting of a
given octane-heptane mixture. The point at which the increaed addition
of octane stops detonation in a specific engine dictates it's octane
rating and the burn rating of the fuel for that specific engine. Lead
was added to boost the octane rating of fuel, but it's not the only way
to increase a fuel's resistance to detonation, thus the newer low lead
fuels we have nowadays.
There are legit additives that keep our engine cleaner nowadays, and
there is no doubt that thye work. Anyone who can remember having to pull
a head off at 50,000 miles for a "de-coke" or whatever you would like to
call scraping the **** off the tops of pistons and heads can attest to
that!

Meanwhile, here's a source I just discovered (but haven't read through
completely) just for fun.

http://www.faqs.org/faqs/autos/gasol.../preamble.html

Some interesting stuff in there.. He refutes what my guy told me about
lead free being more toxic than the old leaded fuels, but of course, as
this guy states in this document, that's not true globally (and my guy
works for Shell outside the US).
Also, he seems to be talking about the resulting product out of ytour
tailpipe, which the document I was talking about agrees with this
osition, merely staing that raw unburnt fuel is more toxic than the old
stuff (IIRC it was particularly dangerous for women and their
reproductive systems) I mentioned that merely because as a group, we, as
pilots tend to get more of the stuff splashed on us than most people (I
certainly do, anyway)
He also explains much more concisely than I have, what exactly an octane
rating is..


Bertie