oil filter magnet

[woody]

i have been fancying one of these for a while

has anyone used one

what are they like

which would you recomend as i have seen a few different types

[TDi90]

not worth it IMO.

[Drift]

Isnt that the point of the filter?

[SteveGoodz]

Isnt that the point of the filter?

Yes, but if you made a conventional filter so that it would block particles in the order of 10-20 microns then the oil would also have trouble getting through as its molecules aren't much smaller and the pressure drop across the filter (due to restriction of flow) would become a problem. You can overcome the pressure problem by using filters with much larger surface areas but the closer the filtration size gets to the molecular size of the oil the bigger the areas needs to be.

These magnets may well come under the category of "snake oil" but the theory of having some method of removing small metallic particles from the oil feed is good. Of course, magnets doesn't work on non-ferrous materials (e.g. aluminium isn't magnetic below about 350oC) like the phosphor bronze alloys used in big end shells.

Indeed if all you want to do is filter out magnetic (i.e. ferrous) particles then just use a magnetic sump plug.

[woody]

Isnt that the point of the filter?

Yes, but if you made a conventional filter so that it would block particles in the order of 10-20 microns then the oil would also have trouble getting through as its molecules aren't much smaller and the pressure drop across the filter (due to restriction of flow) would become a problem. You can overcome the pressure problem by using filters with much larger surface areas but the closer the filtration size gets to the molecular size of the oil the bigger the areas needs to be.

These magnets may well come under the category of "snake oil" but the theory of having some method of removing small metallic particles from the oil feed is good. Of course, magnets doesn't work on non-ferrous materials (e.g. aluminium isn't magnetic below about 350oC) like the phosphor bronze alloys used in big end shells.

Indeed if all you want to do is filter out magnetic (i.e. ferrous) particles then just use a magnetic sump plug.

some good points made there

i like spinner filters like what i had when i worked on scanias
all the heavy particals stuck to the sides

[Range Rover Blues]

Spinning or centrefugal filters are very good bits of kit.  I was looking at a thing called a bypass filter, it filters 15% of the engine oil continuously down to a far finer degree than the stock filter which you leave in place.  The theory is that it will remove the really fine particles that do cause wear, the probelm with a normal filter is that it is a comparamise of filter quality and flow rate.

As sadi a magnetic sump plug would pick up fillings wouldn't it? the idea of magnets on the cartridge is that all the fillings they pick up are automatically removed when the filter is renewed.

Snake oil, definitely applies to magnets on the fuel lines ;)