filtermag
My opinion is it's not worth it. If you have that much metal floating around in the oil, it's time to tear it apart and replace some parts/rebuild it. By the time it gets to the oil filter, it's already been through the oil pump as well.
I've used neodymium magnets before, dime sized ones placed on the end of the drain plugs on three vehicles including a motorcycle (also used to activate traffic lights). These magnets are incredibly strong and they require considerable force to separate if two come into contact with one another. Anyways, neither ever did pick up anything, and trust me that these little things would have for sure if there was any steel present, so I stopped using them, except on the bike.
Nonetheless, if you're dead set on using magnets, I'd recommend the above idea. $40 sounds like a lot of dough, and the little neodymium magnets can be purchased for $2.50 a piece at any science store and I'm sure they're stronger than the filtermag. Another thing is that by using it on the drainplug, you'll be able to see any particles were they to be present, whereas on the filter you'd have to cut it open to examine it.
Just my 2¢
Nonetheless, if you're dead set on using magnets, I'd recommend the above idea. $40 sounds like a lot of dough, and the little neodymium magnets can be purchased for $2.50 a piece at any science store and I'm sure they're stronger than the filtermag. Another thing is that by using it on the drainplug, you'll be able to see any particles were they to be present, whereas on the filter you'd have to cut it open to examine it.
Just my 2¢
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After seeing , and cleaning, the magnets in the differential drain plugs I have been toying with cleaning the oil drain plug really well in a solvent and sticking a small magnetic, as pictured on the threaded end of the plug so it would be in the oil. Was thinking of using a dab of epoxy or JB Weld as added belt and suspenders insurance to keep the magnetic from moving. Haven't done it yet so your milage may vary. Just my two centavos
After seeing , and cleaning, the magnets in the differential drain plugs I have been toying with cleaning the oil drain plug really well in a solvent and sticking a small magnetic, as pictured on the threaded end of the plug so it would be in the oil. Was thinking of using a dab of epoxy or JB Weld as added belt and suspenders insurance to keep the magnetic from moving. Haven't done it yet so your milage may vary. Just my two centavos 

i've had one on mine pretty much since i got it over 2yrs ago. it was $35 and i figured even if it doesn't help anything, it can't really hurt. it doesn't take any longer to service the vehicle with it and it's not like it gets in the way or anything. i'm usually pretty cynical when it comes to gimmicky products (vortex intakes, throttle body spacers, fuel catalysts, etc), but this seemed fairly legit and even if it's not, it was only $35. not saying it does or doesn't work, and i really don't care either way, but it'll stay on mine unless i lose it somehow or i find proof that it may actually be harming my engine, which is doubtful.




