The use of magnetic drain plugs (to catch ferro-magnetic metal particles) is well established.
Is it better to attach a magnet to the oil-filter?
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Sign up to join this communityThe use of magnetic drain plugs (to catch ferro-magnetic metal particles) is well established.
Is it better to attach a magnet to the oil-filter?
No. The point of a magnetic drain plug is to check whether there are pieces of metal floating around your engine. It's not so much to keep these pieces from circulating as it is an indicator of the condition of your engine.
By the time you see an amount of metal deposits on the drain plug, you know that your engine is experiencing excessive wear and may need to be rebuilt/overhauled.
Putting a magnet on an oil filter doesn't make sense because you won't be able to quickly inspect it for the presence of metal shavings.
Borrowed from another forum:
Some magnets are designed for and put on the end of the filter. Inside the filter near that area is the bypass valve, which is mechanical (a spring) and magnetic (steel). If your magnet is strong enough, it will alter the pressure at which the bypass opens (not good).
If you put a magnet on the side of the filter, you may start accumulating small pieces of metal (that's the point). However, you are also magnetizing those pieces, causing them to stick together in a clump. If enough pressure is created, the filter bypass opens and a chunk of magnetic goop could be pulled from the magnet and thrown into the engine. Not only is this piece large now, but it is magnetic, so it can attach itself to parts of the motor and do more damage than it otherwise would (as microscopic, non-magnetic, homogeneously distributed metal).
If you put a magnet on the pan, you can likewise create a ball of magnetic goop. Now you take the magnet off to drain the oil. There is a magnetic pile of goop inside that you expect to drain out with the oil. What if it stays stuck to the pan (is the pan magnetic?)?
(not very concerned about this, but it popped in my brain). A very high-powered magnet near a sensor could affect the sensor readings (or cause it to fail). Given how close it would have to be to the sensor, though, I doubt this would really be an issue.
Warren asked in his comment above: "Why then do the vehicle makers not supply a magnet to re-use every time you change the filter?" The simple answer to that is PROFITS! The faster an engine wears out the sooner they can sell you another one. If a parts fails you have to buy a replacement part. So, does lack of a magnet benefit them or you? (that is a rhetorical question by the way) Most of the time you need to use your common sense to extend the life of your vehicle investment; magnets to trap metal in the oil is one such common sense tactic.
Standard practice on aircraft engines is to cut open the oil filter (on engines with filters, some just have screens) and look for glint, and other signs of particles.
No reason you can not do that on your car filter. I do, and I also do it with my tractor and equipment filters. The tool for cutting them open looks like a big pipecutter, and does not make (many) particles when cutting the can open.
Some engines like the ones on my VWs use filter cartridges which can be inspected immediately upon removal, as they are not in a can.
To address your question, a magnet on the outside of the filter will only provide a weak magnetic field on the inside of a steel can. Therefore, it is better to use a magnetic plug, as larger chips will settle to a drain plug and are more effectively removed that way.
You are all missing the point. Its the metal that you cant see that you are after here. If you could see it.....it would be too late already. by trapping the micron size particles that go right thru a normal filter you lessen the wear on your engine simply because the oil is just that much cleaner. (any cleaner at all is better). JR