I had basically the same experience with an '89 Honda Civic when I introduced it to Mobil 1 around the 100k mile mark.  It went through a quart in less than 1,000 miles -- the whole engine looked moist.  Changing back to dino oil reduced the lose to about half a quart every 3,000 miles.  My '85 Vanagon has been on a steady diet of Mobil 1 since about 44k miles and doesn't leak a drop(superior German engineering!).  I changed my '95 Accord V6 to Mobil 1 at about the same mileage as the van and it holds the synthetic just fine.

Anecdotal information indicates that the engine mileage has a lot to do with the leaking problem.

Chuck
'85 Wolfsburg Westy - 'Roland the Road Buffalo'
In a message dated Thu, 8 Aug 2002 2:01:57 PM Eastern Standard Time, LISTSERV@GERRY.VANAGON.COM writes:

> Date:    Thu, 8 Aug 2002 09:43:00 -0700
> From:    Robert Keezer <warmerwagen@HOTMAIL.COM>
> Subject: AW: Syntheic Oil
>
> I quit using synthetic after it turned my  Jetta  engine into a "Lubri-le=
> aker". Since I went back to dino the leaking has stopped.
> Maybe the brand=
> ? I used Amsoil.
>
> Robert K
> 1982 Westfalia