The answer to 'why is my vacuum greasy' is that a greasy vacuum is usually caused by a buildup of dirt, dust, and debris inside the machine. This can happen over time as the vacuum is used, especially if it's not properly maintained or cleaned regularly.
Some common symptoms of a greasy vacuum include a sticky or oily residue on the hose, wand, or other components, as well as reduced suction power and a musty or unpleasant odor. In some cases, the grease can even leak out of the vacuum and onto your floors or furniture.