i lubed the flex shaft with 3 in 1 oil. since the entire shaft for the length of the extension moves, grease wouldn't travel down to the other end or center very well. white lithium gease works well on repacking bearings, however. for most non motor parts of a kirby (ie rug nozzle lock, handle spring, miracle head solid axles) 3 in 1 oil will work just fine.
will
