Spindles or rotating shafts, often times spin at very high speeds and have a certain level of machining precision associated with them. In order to maintain that precision long term, proper lubrication is required. Either the viscosity for oils or speed rating (Dn factor) for greases, should be selected carefully to match the speed of the spindle. Given the high speeds, the thickener type and cleanliness of the grease might be considered as well to minimize the noise generated from the spindle.