Own a 2007 C350 with approximately 82k miles. When driving smoke entered interior of car and I smelled burning oil. Noticed oil on passenger side valve cover and oil on manifold. Checked oil level and had very little oil still in car (most on floor of garage). I had a mechanic power washed engine and replaced oil filter and filled with oil. Car in garage for two days mechanic has put about 100 miles on car and let idle for about an hour and he cannot find any leak. Anyone ever face this situation?