I will chip in my 2 pesos here, I think from what I read synthetic oil for the Benz is not needed , unless you live in HOT, or COLD climates, Now with saying this I live in Oregon and I use 5-40 Shell Rotella T Synthetic that is used for diesels, I also use dello 15-40, If I owned a over head cam engine of any sort I would use synthetic, mainly because of the quickness the oil gets to the top half of the engine, in all sorts of climate conditions. And If this was my case and I had a very expensive Benz, Lexus. or any other rig which I dont , I have a cousin that works for chevron Gas, and he told me that the oil that everyone uses in the oil refineries...is Mobil 1 DELVAC 5-40 SYNTHETIC diesel oil, they use this in there gas engines, and from what I hear it is suppose to be the best motor oil in the world FOR BOTH ENGINES. You can not just pick it up anywhere I have seen it in TRUCK STOPS, and a few other places, I would try it if I had a lot of dollars in my cars.