Is it recommended to lubricate electric engines (i.e. a dc motor)? I have an electric engine inside a shaver. The engine has started to make some strange noises (not much but still). Lubrication I have here is ordinary universal bicycle oil. I had a vague concern that maybe my oil would destroy the engine's bearings. Maybe I need some special oil for electric engines? Or maybe electric engines should never be lubricated in that way, maybe the grease coming with the engine when it's made should be enough?