Originally Posted by DGXR
Honestly I would argue that it's better to place the magnet upstream of the filter media. This will keep more particles from reaching the filter media in the first place, therefore extending its service life. This assumes that some of the ferrous particles are large enough to be caught in the filter media, which I am not 100% sure of.
Good point, but there are not a lot of good ways to do that unless you have a common filter size that a magnafilter is made for.
The external magnets are nice, but limit the magnet's effect by a huge margin.
I'm not terribly concerned. Plenty of transmissions out there that have magnets directly under nothing but a rock catcher screen filter. How much worse can "after a filter" be than "before basically no filter at all"?
It's kind of a moot point anyway. All of the applications I use them for currently actually have a secondary filter further downstream.
Best one I've done is my KTM dirtbike. Cartridge filter primary allows me to put the magnets outside of the primary filter's media.
That's the only engine oil filter that's gotten magnets so far. Only because of the shared sump.