[CowtownBallin]

Mercedes, BMW, and Volvo like 15W-50 100% synthetic. But from what I hear, only use synthetic if synthetic was used from the start, because apparently synthetic oil will cause leaks because it has lower viscosity. Conventional oils are pretty advanced by now, there's really not much difference, as long as you change it every 3000 miles. I use Castrol High Mileage in my 300E [:D]