"Over time, Mogas deteriorates faster than Avgas"

As a fellow mogas flyer who burn over a thousand gallon of mogas a
year in my plane, and believing the aviation industry is stupid not
moving away from engines requiring 100LL (they should only install
gasoline engines requiring 91/96 or lower octane, or aero diesel
engines into new production planes, if you ask me), I do believe that
mogas deteriorates faster than avgas. The reason is probably due to
different chemical make-up btween mogas and avgas. Mogas's end
distillate is slightly heavier, meaning it has more larger hydrocarbon
molecules in the mix compared to avgas. It also contains a higher
percentage of aromatics hydrocarbon. Those chemical property of
mogas, when oxidized over a long period of time, tend to make the fuel
off-spec more quickly than 100LL.

http://www.generalaviationnews.com/e...olumn&-nothing

Look at the brighter side Jay. If we're paying $1.50/gal less in
fuel, a good chunk of our flying is free. We should simply go fly
more often.


On Sep 15, 1:45 pm, Jay Honeck wrote:

You know, I've heard that ever since I started using mogas in my
planes, but I've never seen a cite, nor have I *ever* noticed a
problem with unleaded gasoline in *any* of my lawn mowers, leaf
blowers, or snow blowers.

I put 'em away in the spring/winter, and start 'em up the following
winter/summer -- and away we go. Same with my Honda Goldwing -- I
top
it off, and it just sits till next year. No troubles.

Can anyone point me to anything that proves (or disproves) the "fact"
that unleaded mogas deteriorates faster than avgas?

On Sep 16, 11:16 pm, M wrote:
As a fellow mogas flyer who burn over a thousand gallon of mogas a
year in my plane, and believing the aviation industry is stupid not
moving away from engines requiring 100LL (they should only install
gasoline engines requiring 91/96 or lower octane, or aero diesel
engines into new production planes, if you ask me), I do believe that
mogas deteriorates faster than avgas. The reason is probably due to
different chemical make-up btween mogas and avgas. Mogas's end
distillate is slightly heavier, meaning it has more larger hydrocarbon
molecules in the mix compared to avgas. It also contains a higher
percentage of aromatics hydrocarbon. Those chemical property of
mogas, when oxidized over a long period of time, tend to make the fuel
off-spec more quickly than 100LL.

http://www.generalaviationnews.com/e...ail.lasso?-tok...

Look at the brighter side Jay. If we're paying $1.50/gal less in
fuel, a good chunk of our flying is free. We should simply go fly
more often.

On Sep 15, 1:45 pm, Jay Honeck wrote:





You know, I've heard that ever since I started using mogas in my
planes, but I've never seen a cite, nor have I *ever* noticed a
problem with unleaded gasoline in *any* of my lawn mowers, leaf
blowers, or snow blowers.

I put 'em away in the spring/winter, and start 'em up the following
winter/summer -- and away we go. Same with my Honda Goldwing -- I
top
it off, and it just sits till next year. No troubles.

Can anyone point me to anything that proves (or disproves) the "fact"
that unleaded mogas deteriorates faster than avgas?- Hide quoted text -

But is there any real future in mogas for aircraft. Its getting pretty
hard to find FAA legal mogas. Out here in California almost all mogas
is prohibited by the STC's.

-Robert

Robert M. Gary wrote:

But is there any real future in mogas for aircraft. Its getting pretty
hard to find FAA legal mogas. Out here in California almost all mogas
is prohibited by the STC's.

-Robert

I spent some time with a friend that is fairly high up the corporate latter
of one of the top 15 oil companies this weekend and we were discussing just
this. He said in the states that do not require marking of gas with or
without ethanol, Arkansas being one of them. That the chance of you buying
gas without ethanol over the long run is pretty much zero. Even in those
states that do have marking requirements the chances of getting a batch that
has it even in an unmarked pump are going to be pretty good.

The hell of it is, Robert, that the mogas is perfectly legal until they dump
it in the delivery trailer along with the prescribed amount of ethanol. The
refinery will sell you all the legal mogas you want so long as you can take
8000 gallon loads.

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford



hard to find FAA legal mogas. Out here in California almost all mogas
is prohibited by the STC's.

-Robert

On Mon, 17 Sep 2007 06:16:42 -0000, M wrote:


...I do believe that
mogas deteriorates faster than avgas. The reason is probably due to
different chemical make-up btween mogas and avgas. Mogas's end
distillate is slightly heavier, meaning it has more larger hydrocarbon
molecules in the mix compared to avgas...

My understanding is that the vapor pressure of avgas is lower than
mogas, to prevent vapor lock at high altitudes. This would make it
keep longer if the storage container isn't perfectly sealed, as mogas
would lose more of the volatile fractions. It would also explain why
avgas plain smells better.

For 2-stroke flyers, there are also concerns about the longevity of
premixed fuel/oil (another endless topic on the ultralight boards).

-Dana
--
--
If replying by email, please make the obvious changes.
-------------------------------------------------------------------------------
They say that politics makes strange bedfellows.
Of course, the main reason they cuddle up is to screw somebody else.

On Sep 17, 3:54 pm, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote:

My understanding is that the vapor pressure of avgas is lower than
mogas, to prevent vapor lock at high altitudes. This would make it
keep longer if the storage container isn't perfectly sealed, as mogas
would lose more of the volatile fractions. It would also explain why
avgas plain smells better.


Vapor pressure of avgas is lower than winter mogas, but it's more or
less the same as the summer mogas these days, thanks to EPA and state
air regulations bringing down vapor pressure of mogas. There are
areas in the country where summer mogas vapor pressure is required to
be 6.5, even lower than avgas.

I believe the stronger smell of mogas came mostly from its much higher
aromatic content compared to avags. Tuluene has a very strong smell.

Tuluene has a very strong smell.


I'll bet if you were a graduate of Tuluene you wouldn't say that.

{;-)

Jim

On Mon, 17 Sep 2007 18:54:09 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote:

It would also explain why
avgas plain smells better.

It certainly does smell better!

The Cubs at Hampton Airfield were STC'd for mogas but now run entirely
on 100LL. A couple of reasons, one of which being that the instructors
complained too bitterly about the smell in the front seat.


Blue skies! -- Dan Ford

Claire Chennault and His American Volunteers, 1941-1942
new from HarperCollins www.FlyingTigersBook.com