I have a 2009 and this has been happening to me for the last 3 years. Antifreeze level would drop an inch or 2 in the overflow after a few weeks. No leaks ( I could find ) nothing on the car or under. Oil was fine and never milky or did I find oily residue in the overflow. Last week at night and it was very cold out -7 , I had the car in the driveway idling . I noticed a very find mist at the time .. like how an exhaust pipe is when u start a car up. I popped the hood and then got a sheet of white paper and held it over the top of the radiator . Sure enough after a few seconds I could see it was antifreeze. The issue I have is that I can not see where its leaking and its leaking such a small amount Im guessing the engine heat is evaporating or cooking the light mist off. This explains why I never saw a leak under the car or on the motor area. Im debating on the Barrs junk they sell. I really do not want to have to mess with a radiator out when its this cold ( Im in Ohio ) . Hope this helps you !