Does very slow oil drain when changing oil tell me something?

[Judge]

When I changed my oil today, (engine warmed) I could not help but notice that after I removed the oil drain plug, I was waiting and waiting and waiting for the oil to finish draining. It was the longest time to drain the oil that I've ever experienced in any car I've ever had. I didn't time it, but I'd say after more than 20 minutes it was still a dribble stream.

Is slow drainage of the engine oill just a characteristic of the 300D turbo engine, or a natural function of the large amount of oil it uses? Or could the very slow drainage be telling me something?

The oil also comes out very black, but I hear that is normal in an old diesel engine.