"Sliker" wrote in message
...
I've got the same engine in my plane, it's an O-320 D2C, but there are
other number series with the same compression ratio in the 160hp
class. That engine is listed on Peterson's mogas STC site as one that
is approved for premium unleaded autofuel. So you shouldn't run into
any problems as far as detonation goes, vapor lock is another issue,
and is different in each aircraft type. Just the other day a pilot at
my local airport said that if the gas has the common 10% ethanol
added, it's vapor lock potential goes up a lot. I'm not sure about
those facts, but I think it has more to do with fuel system design.
Gravity flow systems seem almost immuned to that problem. With wing
tanks below the carb, the best setup is to have fuel pumps at the tank
"pushing" the fuel to the carb. Rather than the more common setup of
the fuel pump in the engine compartment sucking the fuel from the
tank. Peterson's website has a good dissertation about homebuilts
worth reading, in regards to fuel system design to help prevent vapor
lock.

On Mon, 28 Apr 2008 21:13:16 -0700, "Stuart & Kathryn Fields"
wrote:

Well it has happened. Local 100LL is $5.60/ gal and is not expected to
decrease. Is there anyone out there using Supreme MoGas in a Lycoming
0320
with 8.5:1 compression? If so what ignition timing changes were needed if
any?

thanks
Stu Fields

Sliker: Thanks for the answer. Most of the rest of the responses ignored
my question but assumed that I needed either a course in accounting or
fossel fuel economics, or some barroom counseling in an attempt to reduce my
grief over the increased fuel prices.
I looked into the Peterson site and got a bunch of useful info. I've also
found several University studies that have looked into alternative fuels to
and including 100% ethanol. More studying is required.
Somewhere in my excellent memory that I have limited access to, is an
anecdote of some guy who has been using MoGas in his Lycoming equipped
Stinson for quite a few years. The ethanol aspect was not discussed and his
history certainly started before the ethanol additive.
For the very near future I will be mixing Supreme with 100LL until the LL
runs out. When I switch to 100% Supreme, I will be hovering my helicopter
for a few hours and keeping track of the CHT, EGT, MP etc.

Thanks again for useful response.

stu