Alembic advises using pure lemon oil. Be sure to get pure oil and nothing else, no waxes, fillers, fragrances, NOT lemon pledge. I got mine from a health food company on the net. Rub a small (couple of drops) amount into the neck, let stand for at least 15 minutes, then wipe off. I'd recommend putting the old strings back on for a few days as the oil seems to come off on the strings right after oiling. Do this about every six months or so.
Bill, the guitar one