I have a 2007 lincoln mkz, that shows a little smoke fron the drivers side coming from under the hood, and it smells of possibly the radiator or oil, I have taken to the dealership twice to be told they can't find anything. When I drive it for at least 10 to 15 minutes on the expressway and get to a light and sitting idle, I can see some smoke from time to time. It came thru the vents just recently. I can't understand why the dealer can't find anything.
Take it to a general mechanic, ask them to do a cooling system pressure test and check for any small oil leaks onto the exhaust system, this should find the problem, the dealer is just not interested, fairly typical these days.