Dave, you do not need a preservative for hemp oil … what you need is an antioxidant … as Belassi said, you can add Vitamin E (tocopherol) or a CO2 Extract of Rosemary. Either will help in your hemp oil becoming rancid.
Belassi and MarkBroussard, Thank you very much for the advice. I will try both vitamin E and/or the extract of rosemary and play around with the ratios. I hope to find a way to be able to keep it out of the refrigerator and keep it in the bathroom for convenience. Thanks again!