Well, in a purely subjective view;
After reading on forums and talking to people that fly RC-Heli, they often have bearing problems in their OS engines. Changing bearings 3-5 times on a season is not uncommon from what I've heard and they run 20-23% full synthetics (low visc).
Some have tried 1-2% castor in their fuel and been able to go down to 18-20% of total oil % (low visc + castor). Even doing so they have been running a full season on the same bearings after that.
But, in a objective view;
Has any of you that have all of this fancy equipment done a comparison under microscope to see how a castor oil looks like?
My bet is that although the castor might have a certain viscosity when measuring a couple of cc, itīs molecular build is far from regular compared to a synthetic oil that is precision built to specification.
Itīs noticeable in lower rpm how well the engine seals up, it makes big difference in bottom torque as the time the oil is subjected to pressure increases and the pressure is lower inside the engine so there is less increase in viscosity.
What I've noticed (again in a subjective manner) is that the more synthetics you run the more oil is needed to seal the engine and/or increasing the viscosity of the synthetics will produce more drag (increased spool time) compared to castor before itīs on par when it comes to sealing.
But thatīs just what I've noticed...
