Although I'm sure you were jesting, the oil filter isn't the registered component
Although I was jesting, the atf has ruled that any component of a silencer is also a silencer itself, and thus an NFA "firearm". According to the letter of the law, they CAN charge you with illegal possession of an NFA item for owning an oil filter.
"Oh but they'd never do that, that's ridiculous!"
Yeah, ok buddy, keep those blinders on tight.