Fuel selection for our engines can be a
problem. Some use the same gasoline that is used in their cars. My
friends and I have tried this, but it really stinks when burned in
our model engines. This is probably due to the low temperature that
these engines operate at (especially the hit-n-miss) and the
somewhat rich mixture required by smaller engines. We came to the
conclusion that it also carbons up the valves and spark plugs far
worse than the camp fuel we had been using.
Most model engine owners are using Coleman Camp fuel with good
results. My Plunket Jr. engine (not a hit-n-miss) has higher
compression than many model engines and I noticed that it made some
strange knocking sounds that were not mechanical, so I decided it
must be detonation. Wondering what the octane rating is, a friend
called Coleman and was informed that the octane rating is only 53.
No wonder that it knocks! Knowing that methanol (used in may race
cars) has a very high octane rating and burns clean, in 1999 I went
looking for a source and found it at an automotive speed shop. My
Plunket Jr. and PowerHouse engines love running on alcohol! Valves
and plugs stay clean, and there is no more knocking, but cold
starting can be somewhat difficult.
I continued using the Coleman fuel in
my antique model hit-and-miss engines because they are lower
compression and don't knock on the low octane camp fuel. Over time,
I finally became disgusted at the fine lint particles in the Coleman
fuel which was causing all manner of problems maintaining a proper
needle setting over a period of time. I began filtering the fuel and
installing in line fuel filters on my engines. One day while at a
Walmart store around 1997, I noticed they had camp fuel called Ozark
Trails on the shelf next to the Coleman fuel. I decided to try a can
and see how it compared to the Coleman fuel. Upon checking, I
discovered that it was clear as water and had no trace of lint
particles. It ran just fine in all my hit-and-miss engines. I told
my friends about the Ozark Trails fuel and they gave it a try. Now
they use it too and we all agree that it even has a better exhaust
smell than the Coleman.
One day I got to thinking about the fuels I was using. The camp fuel
is easy starting but carbons the valves and plugs, while the alcohol
burns clean but can be hard starting when the engine is cold. I
wondered if I could blend the two together and get the best of both.
I discovered that up to 30 parts Ozark Trails camp fuel will blend
with 70 parts of methanol. Any amount of camp fuel over 30 percent
will not mix and will stay separate. An engine will start just as
easily with this blend as with straight camp fuel. After running the
70/30 methanol/Ozark Trails fuel for more than 100 hours, I found
that the valves and plugs stay really clean. The spark plugs in my
Plunket Jr. and PowerHouse engines run almost a frosty white, no
carbon deposits at all! The fuel needle setting needs to be a little
richer and a tank of fuel will not run quite as long as camp fuel,
but this could hardly be of concern. The methanol raises the octane
rating of the blend to a high level. I think it is the best of both
worlds, as they say. Don't use these fuels in your lawn mower or
car, models only!
Addendum October 2006 - I have been running the 30/70 fuel in my
V-Twin engine since it was built in 2003 and also in my new V-Four
engine. After many hundreds of accumulated total running hours in
all my engines, I have found no negatives at all with this fuel
blend, only positives.
Addendum June 2008 - Wal-Mart discontinued the Ozark Trails brand
fuel earlier this year or late last year. If anyone finds a good
substitute (not Coleman) please let me know. I am now running
straight methanol in all of my engines. If you decide to use Coleman
camp fuel, you should at least strain it through a couple of coffee
filters to remove the lint.