Weird goo on door sill?

["Will @ The GMS" <will@givemeslack.com>]

Hello list.

For a while now I've been noticing this weird goo which keeps appearing on
the door sills of my 2000 Jetta GLS.  It has the consistency of turtle wax
or some type of grease.  At first I thought it was from where I had the car
detailed and hand waxed a few weeks back... but it keeps showing up...
apparently dripping down from the underside of the doors.

Anybody know what this stuff is?

I haven't had a chance to get down under the door and check out where it may
be coming from.  It's awfully annoying though because it invariably gets on
my pants leg and I enter and exit the car.