Yes, there are two possibilities, one is wave tank oil, the other is engine oil! Wave tank oil is more likely, because wave tank oil also needs to be cooled like oil, it may be that the pipe in the cooling system leaks oil, and then the oil is mixed into the antifreeze! If it's oil, it's a washout. 2010 model E300 imported short shaft, 50,000 kilometers when the 4S shop changed the transmission oil once