The oil filter is itself a babbitt magnet, or accumulator.  Probably
makes more sense to attach magnets to the sump of a manual
transmission/differential, which has far more direct
ferrous-to-ferrous interplay.

Casey
Olympia, WA
Biodiesel: "I drive in a persistent vegetative state"
'87 300TD intercooler (211k)
'84 300D (205k)
Gashuffer:
'89 Vanagon Wolfsburg Edition (186K)