On 10 May 2006 13:24:27 -0700, "xyzzy" wrote:

For example in their article on fuel, Aviation Consumer had a sidebar
on mogas saying it wasn't as good as advertised. They said several
shop owners told them that when they get engines or cylinders in for
work, they can immediately tell if the owner is running mogas by the
corroded camshafts and deposits on the valves and seats. These shop
owners claimed that the extra overhaul costs eliminate the mogas
savings, and attribute it to the "varying additives" used in mogas and
to the fact that most mogas sold doens't really meet the ASTM standards
dictated by the STC.

Junk science from the aircraft maintenance industry. Since auto gas
STCs generally prohibit commercial operations, you can expect that if
an airplane is being flown on auto gas that it's probably going to be
on weekends by pilots who have to work for a living the rest of the
week. That's the kind of operation that has already been documented to
cause corrosion on camshafts, regardless of fuel. And as for deposits
on valves, how could auto gas deposits be any worse than the deposits
caused by 100LL? Lead deposits have been documented to cause valve
burning, valve sticking, ring sticking, spark plug fouling, and
in-flight engine failure. That's a major reason why we're running
mogas. A claim like that might make sense if they noted a lack of
deposits as being the indicator of auto gas operation.

I'd be more impressed if these people would publish objective,
scientifically controlled studies instead of anecdotal observations.
As it happens, the only people who have done studies have found no
problems with auto gas.

It is noteworthy that the FAA has given its blessing to 82UL avgas,
which, being based on auto gas, contains no lead. It's FAA approved,
so it must be ok, right? Of course I doubt that anyone now living will
ever see it at our local airports.

And then there's NASCAR. After years of noise from environmentalists,
NASCAR has announced that they've developed and are beginning to use
an unleaded alternative to the leaded racing gasoline they'd been
using, which was essentially the same stuff we fly with. Once the
environmentalists get through with NASCAR, don't you wonder how long
it'll take for them to draw a bead on us? They may ask that EPA start
testing air quality around airports just like they asked the EPA to
test air quality at NASCAR races. EPA says they're not interested in
doing anything about avgas, but that could change with a single
election or a single court decision.

RK Henry