'An electronic pH tester is best, but you can also use phenolphthalein solution (from a chemicals supplier).'


I disagree 100% with this. PH meters are unreliable with something like oil. They measure the PH of aqueous solutions only, reliably, from what I understand. And oil and alcohol isn't it. I used one briefly and virgin oil titrated at 1 and nasty oil that in reality was a 8 or 9 also titrated at 1. No matter what oil you used it was always 1. I use turmeric which is cheap and can be found at any grocery store with a spice rack.