In my experience, the various oils and "fretboard conditioners" (which are just repackaged lemon or mineral oil) usually cause more problems than they solve. So, I stopped using any of them years ago. An alcohol-dampened rag will clean a fretboard up nicely, and your fingers will keep it oiled more than it needs to be. Unless you don't play much. In that case, lemon or mineral oil is good once a year or so.