After having the rear of my new 2005 XK8 convertible up on jack stands for about 24 hours, I found a largish (about 3 inch in diameter) pool of rather viscous oil on the driver-side (US) door threshold, almost directly beneath the outside rear view mirror.

Let's see, that's a compound, complex, run-on sentence, isn't it!

Anyway, the oily substance had little or no smell, and was perhaps yellow-green in color.

The top hasn't been raised or lowered in a few days. Indeed, the only action of the car was to start it and back it out for lifting the rear.

Any thoughts?

 

If you look at the post just below about a mysterious leak, several of us suspect power steering rack leak. When I had this problem it leaked from the same place that you're describing.

 

My leak/oil puddle was on the inside of the car; on the door threshold.

 

See where my steering rack leak was coming from in this video at 3m 10s.