SGC,
oil polymerization may follow different paths. One follows oxydation, and adding or finding antioxydants in oil helps avoiding oxydation and accompanying polymeryzation . But polymeryzation may depend from other causes, as temperature or chemical/mechanical tratment. So the presence or not of antioxydants, as tochopherol ( vit E) does not exclude the possibility of enhancing the viscosity with appropriate treatment.
Rising the polymerization by oxydating methods is to be avoided for closed crankase engines since it is invariably accompanied by an increase of acidity of the oil, that leads to corrosion after a hundred hours of internally recycling circulation. This is not clearly our case, so oxydating polymeryzation could be accepted.
As for olive oil, it starts with the highest viscosity between edible oils before any treatmen, but is the less prone to "enhancements". I don't know much of rice oil, but it could rise in viscosity due to the presence of double carbon bonds, perhaps the suggested modification does not work for it.
From your reply can I argue that you were the first here to try and suggest olive oil? If possible, in a very short way, could you resume your modification procedure?
Ugo