Oil leak on cold nights?
 

Late last winter I noticed that I was getting a little bit of oil on the garage floor overnight it was such a small amount I was just going to have a tech look at it when I got the oil changed. However, when it came time to change the oil the leak had stopped. No leaks all through this past summer and now as the nights are getting colder, the leak is back. Basically, when it falls below 45 at night, I get a little drop of oil on the floor. I've had the head gasket replaced at about 90K and the milage now is coming up on 126K.

Last night I opened the hood after my drive home to check for the smell of hot oil. As odd is it may sound, sniffing at the corners if the engine, the distinct smell if hot oil is coming from the rear passenger side. Given the vague description, any idea as to what would be leaking?

BTW, this is a 96 C280

Thanks,
Brad

Valve cover gasket, rear main crank seal, transmission front seal.