I've used individual magnets and a PAIR of FilterMags for 4 yrs or so, no issues.
But when you select individual bar magnets, be sure they're about 3/16" wide max, otherwise
the won't stick fast to the radius of the filter housing and may 'rock' a little, this means
some or most of the magnetic field is not cleanly coupled to the filter housing thru to
the inside. It seems counter-intuitive, but long narrow magnets generate a strong narrow
field that picks up well inside a filter!
ALL magnets have a specified max operating temp spec (& currie point) so if you chose low temp neodymiumOR
samarium cobalt you may not be happy after a while. Realistically you may lose 20% or so.
(Low temp magnets have a currie point of about 350F where they die completely. In a engine oil application
you won't hit that on a family hauler)
Min operating temp for most is 175F, then 200- 250F and up. The kicker is if you overdo it and pick the
highest possible, they'll be weaker out of the box as a trade off for really hi operating temps.
For filter applications you wanna be 200F to 250F, not more then that.
TIP: If you order magnets, be sure they're magnetized thru the sides, not the ends. In the old days
kids magnets were only strong at the ends. For filter use you want the N / S poles to be on the long sides
of the magnets you chose ("magnetize thru it's thickness). Manufactures may offer magnets with different
Take a look at some the pics in this PDF:FILTERMAG vs HOMEBREWhttps://app.box.com/s/uxvu8dmscf5wcgftutdm0ejqwgn86tw7
A good place to order magnets is KJ Magnetics on the web.... or is 'JK'? close enough! gotta check again..