Maybe the oil is spraying out 'perfectly' from under the oil filter gasket, not leaving any drips or stains.

Does the oil pressure gauge usually drop to 0 at idle, or only in this situation?

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma