https://www.cvs.com/shop/cvs-health-min ... id-1011823
I swear a 16oz. bottle of drugstore mineral oil was less than $3 not that long ago (...finds out it was 15 years ago, turns to dust...)
And re: olive oil, here's the late, great Frank Ford:
http://frets.com/FretsPages/Musician/Ge ... ing02.html
Frank Ford wrote:Some players talk of "feeding" the unfinished surface of the fingerboard with oil. Fingerboards are not actually hungry and don't really need to be fed, but a light coating of oil gives them a finished and clean look. If you do choose to oil the fingerboard, do it with care. Use a tiny amount of lemon oil or mineral oil on the rag, wipe it on the fingerboard, and then wipe it all off. You don't want to saturate the fingerboard, and you don't want a lot of oil running down into the fret slots. If there are cracks in your fingerboard, consider having them filled professionally, and don't get oil in the cracks. Generally, you'll want to stay away from linseed and other natural vegetable oils, which become sticky and gummy over time:
This kind of fingerboard cleaning should be a once-a-year event, at the most. Too much scrubbing and oiling can easily do more damage than good.