Thanks Casey,

I also know that in the case of model airplane motors, castor oil is
preferred for bronze bushing engines and the older engines with cast iron
pistons and steel liners as opposed to the new aluminum, bronze, nickel
configurations.  The case being that if a motor has a lean engine run the
castor oil offers more protection and has a higher operating temp as
compared to synthetics.  Interesting.  In the case of percision aerobatics
for control-line competition, if you have a lean run on the older engines,
you will lose some compression because the piston increased its size as the
temp rises and thuse you ultimately lose torque. So, castor oil is preferred
for those motors.

This probably speaks to the common procedure of breaking our Lycomings and
continentals with castor oil.

Question:  Why do we change out the castor oil for the other oils?  Is it
because of the additives and the ashless dispersant and to prevent castor
oil buildup in the motors?

Bob Smiley
N94RJ