Lanny- You've confirmed what I suspected - When I pull those cartridges out and see how filthy they look, I've always hoped I was looking at the dirty, upstream side.

The prevailing suspicion seems to be that Guyton's filter was poorly made - but what if it started out perfectly good? What happens when a properly working filter becomes totally clogged? Is there a bypass mechanism in the engine to keep oil flowing under those circusmstances, or does the filter collapse inward as this Chinese one seems to have done? Maybe those symmetrical holes were caused by a support structure that helps the filter keep its shape, but which became overwhelmed. Maybe we can't see it because the filter pops out a little when the engine stops.

If this was an episode of CSI on TV, those exit wounds would have led to an autopsy by now. It's time for Guyton to cut this thing open.

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