It could be but molybdenum disulfide normally used as the base of that additive is not magnetic. This selection is by design because you want that additive to stay solvent and not plate out. I am not sure what the gunk on the drain plug is, but there is a fair bit of it. I wonder if there is anything else that is ferrous in the oil? It just might be very fine particles from the bearings due to normal wear. If that is the case I will keep changing the oil ever 5 K to 10 K. It takes 20 minutes and cost $11 bucks so no big deal.