TIL: The hole on the back of a tuner is for lubrication. : r Guitar Gotoh Classical Guitar Tuners, With ivoroid knobs What grease would you use to lubricate tuners on a classical guitar. I found using Petroleum Jelly (vaseline) too light. Any suggestions would be great. EVH Nut Butter Guitar Lubricant Don't Replace Your Strings Restore Them. Every time you play, your strings collect sweat, oil, and buildup that slowly kills your sound. Big Bends GEM TONE String Wipes bring them back