Lonnie, I've been using Mobil Clean 5000 5W-20 in my '99 Taurus with the 3.0 Vulcan (2V pushrod) motor for a couple of years, with no downside that I can see. I haven't done any UOAs as it's our winter hoopty, but the car seems to like it just fine. I've recently come into a stash of MC 5W-20 and I'm going to use that from now on.
I've also switched my niece's '99 Contour with 2.0 Zetec to PP 5W-20 (she puts on a LOT of miles) and my sister's '96 Taurus (same motor as mine) to MC 5W-20. Both of those cars seem to like it as well.
