Oil leak - any ideas?

[Quadcammer]

any number of things, including the valve cover seal, the spark plug tube, cam plugs, oil getting into the intake and leaking through the plenum connectors, etc.

You gotta clean it all up really well, then go for a drive and see if you can pinpoint.

[kk2002s]

Agree clean to determine origin
Thing with fill tube, only if you were adding oil would that come into play
What about before last week, were you seeing oil?
When car is running how is the vacuum on the oil fill cap when you remove and does the engine run differently?
If you have a crack in your fill tube, that would be a vacuum leak similar to removing the fill cap.