As it turns out, it is the oil filter gasket - I adjusted it tonight because it was not all the way up against the filter housing surface when I changed the oil a couple months ago. It was holding oil, but showed a little leaking, and I didn't think it was right but left it then. I figured I would correct that tonight, but had to coax the gasket up one more notch above the threads of the filter housing to seat it (what I believe is the way it's meant to be).

Possibly I damaged it? Made it too loose/tight? It is a NAPA product, not MB - what do you think?

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Francis E. Abate
Automotive Restoration & Preservation
Sheet metal, trim and upholstery