Lately, I've been seeing oil spots where I park my 2013 C300. The underside has a large oily stain on the plastic splash guards where the oil plug should be. However, the area around the drain plug and oil filter shows no signs of leaking. The oil levels on my dipstick also look fine. The oil's smell does not smell like motor oil to me, but It could be because I use synthetic oil. Does anyone have any idea where the oil is coming from?

 

Have you looked at the top end like around valve cover? Also, possible transmission oil?