During the last oil change, I noticed an area under the engine of my 2000 S80-T6 with oily residue. I don't know what the name or purpose of the part is. The linked photo shows it well and was taken of the area under the driver's side section under the engine. If anyone has some insight, I'm thankful in advance.

http://www.brickboard.com/GALLERY/images/10391.jpg

The round black device is called a viscous coupling. The axle shaft goes through the middle and there is a replaceable seal. You have to remove the axle to access and remove the coupling.

I have a 1500 km trip scheduled before I'm able to book the car in for repairs. Planning to have it in the shop about three weeks from now. Is it ok if I just keep an eye on tranny fluid? What's the potential side-effect to not fixing this leak in a timely manner?

If that is indeed the viscous coupling, no tranny fluid is envolved. I have never seen a VC unit drip fliud. If it looks like motor oil, I would suspect oil dripping down from the turbo.

Klaus
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There is no present time, just the past and future

At the time of the oil change the power steering fluid had to be topped up. Could that be what's leaking? (I've included a second phot from under the car.)

That's a lot of PS fluid. There are 2 oil cooler lines in that same general area, if they leak it will be in front of the block and behind the radiator.

Klaus
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There is no present time, just the past and future