Bob, I put 4 rare earth magnets around my filter and I think they do work. I had used these on filters for my Mooney 201 when I had the plane and the
oil analysis that came back (before & after) showed significant improvement.
Rare Earth magnets aren't cheap. Usually, you'll need pliers to pry them apart and if your finger gets pinched between them, you could get a blister. These are the ones that work...