An update to this... The blast of oily smoke was the pressurized oil coming from the unvented crank case forcing its way into the cylinders, as this was the new path of least resistance. Days (not weeks) after my last post, she froze up again and spewed oil out the fill cap. I called the shop and was told that it wasn't cold enough out for this to be happening, and that I must have a massive amount of condensation in there, despite changing the oil. He advised me to crack open the dipstick and drive like that for a few days to let the condensation out. I have been driving for a few weeks with my dipstick out a touch, for fear of another damn freeze up and $700 bill. I will fully insert it when temperatures remain above freezing. All the bmw shops in town talk about how common the ccv freeze-up is. They typically get around 100! X5's per dealership per winter with that problem... Perhaps all X5's that are sent to Canada should come from the factory with the dipsticks out a bit. The Ultimate Driving Machine.