What's the damage from doing this?

WarmAndSCSI

I'll find pieces of o-rings from working on valve stem seals on the car, valve stem seals, chunks of RTV sealant from where a bead was in excess. Stuff like that.

What you've gotta understand is that it's not the end of the world if you drop something down into the oil pan... like I explained before, such debris would have to make it through the oil pickup screen, through the oil pump, and through the oil filter in order to cause any damage. All of the wear surfaces within your engine are basically sealed under pressure, and the pressure is always pushing "out" so really nothing external can get between a bearing and a journal, for example, unless it was already between the two surfaces during assembly or it somehow makes it through the entire pressurized filtration system first.

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