from Clarence Lee
"You say you never use after-run oil in your engines due to using
fuel with partial castor content. This is a big mistake many fellows make.
Although the castor does help the rust situation, it also turns to shellac over
a period of time.
Even after setting for only a few weeks it becomes thick and
"gooey" which causes the balls in the ball bearings to slide rather than roll.
The result is flat spots on the balls, over heating, and eventual failure.
Many rear bearing failures, especially when the ball retainer comes apart, are
due to congealed oil."
A lot of companies sell so-called after run oil. None of these companies
actually make oil, so they are simply repacking an already available product at
a greater cost to the consumer. I like Marvel Mystery Oil, but it has not
prevented the bearings in my engines from rusting. I don't know why it
doesn't work... maybe that's the mystery. But it has a nice minty scent
which is important I guess.
Marvel Mystery Oil works fine as a short term protective agent in
your engine. But before you put protective oil in the engine, you have to get
all the fuel out. At the end of the day, some people drain their fuel tank
and then run their engine at full throttle until it quits.
This practice does
not burn all the fuel out of the engine. Why? Because it takes a lot
more fuel to run an engine at full throttle than to run at idle which means
there may still be fuel in the engine, but not enough for the engine to run with
the throttle wide open.
To really get the fuel out of your engine, run the engine at full throttle until
it quits. Then reduce the throttle to idle and repeatedly start your
engine and let it run until it quits. Keep starting the engine until it just will not
kick over any more. Then pour a liberal amount of oil in the carb (full
throttle setting) and turn over the engine several times. Put more oil in
and turn the engine over some more. Do it again.
The after run oil manufacturers say, "Just use a couple drops."
If the engine were open and you could actually see the oil going into the
bearings, do you think a couple drops would be enough? When you put the
oil in the carb, you can't be sure it's going where you want it to so use
Oil is cheap compared to bearings. Wrap your engine in clean
rag held in place with a rubber band so the oil does not drip all over everything
and the engine will be safe for a couple weeks.
For the most part I do not use after run oil because I use fuel containing
castor oil. I run the fuel out of the engine at the end of the flying day
and clean the outside of the engine when I am cleaning the plane. So far I
have not had a problem with rusted bearings with the exception of some engines
that were stored for an extended period and supposedly protected by filling the
crankcases with Marvel Mystery Oil.