The KitchenAid mixer comes with a small bottle of vegetable oil that is designed to help keep the mixer lubricated. The mixer should be lubricated every six months or when the mixer starts to sound louder than usual. To lubricate the mixer, remove the bowl and the flat beater, then remove the screw holding the gearbox cover. The cover will come off, exposing the gearbox. Pour there a few drops of oil on the gears and replace the cover. Replace the bowl and the flat beater, and turn the mixer on at the lowest speed for a minute.