Just buy it from Walmart and get a syringe filter .22 and filter 100ml into a sterile vial. You van find all of those things thru a sponsor or very easily on the net. Get a 20g syringe 18g needle, then use a caulking gun to filter thru the .22 syringe filter, if not it will hurt your hand and take a while. Whatmans should do 100ml per filter, other brands not so much but becareful because the filter will blow out from pressure. If you see if losing shape or any thing odd, stop using it.
Now you will have sterile oil, safflower is commonly sold at local stores and works great. After you decide how much oil you want to add, you will probably need to transfer you test and sterile oil to a larger bottle. Trasfer both, put a pin thru the rubber stopper but not touching the oil, and put on the stove in a pan, keep the heat low, swirl the vial until it's a perfectly clear solution again.