Most excellent reply by Bill Daniels..
May I add that we recently upgraded our O-540 from 235HP to 250HP with an
STC, the STC for the upgrade specifically prohibits use of auto fuel. There
are two parts to the STC, one to upgrade the engine, the other to install
that engine on the Pawnee airframe.

BT

"Bill Daniels" bildan@comcast-dot-net wrote in message
...
I don't have the whole answer but I'm working on it. Here's what I do
have. Many Pawnees have been successfully using MOGAS for rmany years all
around the world, but.....

1. The Lycoming O-540 235HP engine has an STC for MOGAS in several
airframes.
- (The engine, propeller and airframe have to be STC'd together as a
unit.)

2. Some, but not all, Pawnee airframes with the Lyc O-540 have MOGAS
STC's.
- Pawnee D airframe doesn't.

3. No MOGAS STC allows use of fuel containing ethanol - it does bad things
to aircraft fuel systems. Many, if not most, problems related to using
MOGAS have been traced to ethanol in the fuel.

4. There is an increasing number of reports of MOGAS containing ethanol
sold at airports for use in airplanes.

5. There is suspicion that ethanol is being added to gasoline earlier and
earlier in the distribution channel so that even if you have a deal with
the local petroleum distributor to deliver MOGAS without ethanol, he may
still unknowingly do so. Best advice is to test each batch of fuel for
ethanol before using it.

6. Many states or localities mandate special automobile fuel blends to
fight air polution. STC's for MOGAS do not take this into account.

So, while MOGAS can work fine in a particular Pawnee, the owner/operator
has to assume the responsibility to insure that all fuel used meets the
STC requirements.

Bill Daniels



wrote in message
...
Our club in Indiana is looking for advice and / or experience in
converting Pawnee Tow planes to run on motor fuel. Any comments or
advice would be gratefully accepted .