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Magnets in the oil pan

This isn’t a bad idea, but the magnets can only be removed when you take the whole pan off, not just during an oil change. You also have to put one in an area that the oil with literally gravitate to so it’s got a better chance of grabbing the metal particles, while not blocking good flow to the pickup, which usually also located in the best place to grab the most oil.

There’s a product I found for my Harley’s oil filter. The “Motion Pro Filter Magnet” is a magnetic washer (very strong!) that is placed with the hole over the hole on the filter and nabs any metal particles going by. It’s $10, but it’s reusable, and doesn’t block oil flow. Works great on my Harley and my Dodge Ram

They also make external magnets that clamp onto the oil filter, but they tend to be pricier.
There are magnetic bearings that you can drop into the new oil filter at each change, but you have to get one for each oil change, as you don’t go fishing them out unless you enjoy the mess of cracking a dirty oil filter open.

Allison transmissions used on diesel powered GM pickups and many large commercial vehicles have two filters, one internal filter and one external spinoff type. The external spinoff filter has an external magnet and when replacing this filter the magnet is transferred from the old filter to the new transmission filter before it is spun onto the transmission.

Yes, the external magnets get transferred from filter to filter, but the reason I don’t like external magnets (besides the price) is that they can, and do, fall off. ALOT! Also, because the oil filter has something of a cooling effect, though this is more for motorcycles and air cooled motors, than cars. You put a big honkin’ magnet that takes up 30% - 50% of the surface area on the oil filter and it keeps that cooling effect from happening.

I’m familiar with the use of magnets in transmission pans. I have a hard time believing there would be enough ferrous material in the oil of a modern engine that would not be trapped by the filter to warrant an engine magnet. Let alone a situation that would require it to be easily accessible to remove the buildup. If that is the case, I suspect you have more to worry about than the accessibility of the magnet…

I’d rather just change my oil regularly. And why would one want to in any way prevent any particulates (ferrous or not) from being carried by the oil into the filter element, which gets changed with every oil change?