Um, I have an F55 with a 2.8 diesel which smokes and drips small amounts of oil from engine block (crank case?) breather tube.
One suggestion was that the engine (rings) are tired, another is that I have used the wrong grade of oil...
It doesn't affect engine operation at all (as far as i know LoL) but is a bit of a piss off when sitting in traffic. Oil coming from tube really is just a centimetre radius stain on ground after standing overnight.