Thanks for your help in advance. I've a 2008 Peugeot DHI 16 stick shift car, and all of the sudden even without overheated, I found oil mixed with the coolant in the reservoir. It is not a milkshake color mixture, but pure black oil. (Note: there is no oil cooler or gear oil cooler in that kind of cars.) I need to know the reason and how to repair, if you please. Much obliged!