Maybe I've just never noticed this before on any of my other cars: I recently bought a 2003 Taurus/Vulcan engine and when I went to change the very dirty oil noticed bubbles on the "top" of the filter - that is: the side that's open to the engine. Yes, I drained out the oil from the plug on the bottom of the pan before I unscrewed the filter. Any ideas if that's a concern? There doesn't seem to be discoloration (like water in the oil).