I do have a disk cleaner, which I use with Klean (an old utility that simply spins dfX: for a few seconds). The problem is that disks can go bad in the same sitting. And by bad, I mean unformattable. All my Amigas have had problems this way -- and old Mac, PC or ST disks have stayed basically reliable. I will open up a drive and try the clean and oil. Thanks.
(I've eBayed my way through a bunch of drives, and would like to find an alternative strategy.)