TDI 2.0 BRD qualmt und stinkt | Posts 16+

"Interesting theory, especially because it would explain several symptoms at once. The fact that the smell of oil and the fluctuations in idle speed only become more pronounced when the engine is warm at least supports this."

I wouldn't be completely certain about the diagnosis until the connection can be clearly proven. Especially with the 16V TDI engines, there are several possible causes that can point in a similar direction. A crack from the glow plug hole into an oil channel would be a rather difficult fault to confirm unless the cylinder head is properly inspected.

I also find it interesting that it hasn't deteriorated much over tens of thousands of kilometers. With a normal oil leak towards the combustion chamber, one would generally expect it to become more noticeable over time.