Possibly head gasket.
it could be coming from a valve cover gasket that is leaking
oil leaking on your spark plugs in your Lincoln LS because you have a leaking valve cover gasket.
Head gasket could be bad
The only thing that could leak oil in that area is the valve cover gasket.
Core plug - Wikipedia, the free encyclopediaCore plugs, sometimes wrongly called freeze plugs or frost plugs, are plugs that fill the core holes found on internal combustion engines. ...en.wikipedia.org/wiki/Core_plug
Well 9 out of 10 times this is an indication that you have oil leaking past the valve guide seals and leaving an oil residue on the plugs.
Try replacing oil filler cap.
Were the spark plugs oil fouled? If so it can be a valve cover gasket, oil would be leaking into your spark plugs.
it could be leaking from some were above and its driping on the pan causing it to look like its leaking from the pan or if you over tourk the bolts it will warp the pan causing it to leak
it is leaking from the valve cover gasket. when the car sit long enough, the oil will leak down to the plugs.
Probably a blown head gasket. Get a technician to look at it. If it is, it will be a major ordeal.
The VALVE covers must be leaking oil, If it is only on the threads.