Does anyone know what this could be? I can't see any visible leaks anywhere. Oil feed and return are all clean. I could smell a very slight burned oil smell during the summer when at a stop, but today I used the heater for the first time and when I came to a stoplight it was much stronger than normal. I popped the hood and there was no smell whatsoever in the engine bay. The temperature outside is about 45 degrees and I also noticed more vapor from the exhaust. No oil or coolant smell that I can detect from the exhaust. This is the first time I've driven without a catalytic converter in cooler weather. Would this have something to do with the excess vapor? Any ideas? I'm thinking it might be the beginnings of a leaking headgasket.

 

Does anyone know?