Yes although not in my porsche, and yes switched back to dino. And yes
the leaks went away, but I always wondered which seals were allowing
the oil to escape. I use mobil 1 15-50 in my 1987 944 na 102,450 mi.
daily driver,no leaks, also in my 1986 911 carrera 43,450 mi. track
junkie smile maker no leaks.
I talked to a p-car mech. one time who said oil leaks are never
normal, some are just better tolerated than others.
don

I had an 80sc that would leak out the 15-50 only when I stored it for
the winter but soon as I started driving it again it stopped leaking.  
Mobil 1 has some very slippery properties that allow it sometimes to get
through gaskets and seals that either are dry or need replacing.   I use
Mobil 1 on all my cars and never had a failure yet.  A few drips won't
kill ya!  Chris