And what about magnets on an oil filter

[DieselPower]

A drain plug magnet should do the same thing. When I was young ( a long time ago) we put cow magnet on the fuel lines of our cars 100% better millage.20 years ago the thing was magnets on the waterlines of your house 100% better water now we put magnets on the bad knee joint 100% better in 1 hour. This sounds like a good idea my oil will last 100% longer.

Actually it has nothing to do with making your oil last longer. The idea is to catch any metallic particles to small for the oil filter to catch thereby preventing it from circulating through your lubrication system. Magnets on drain plugs of medium/heavy trucks is very common. Since the type of engines we are talking about do not have them the filter is a good place to stick one.