European engines are spec'd so differently from what we're used to here in North America that what normally works, the common sense stuff, none of it applies with a Sprinter. You have to think European. In Europe, the engines are designed, and then the oils are manufactured specifically for the engine. It's beginning to change a little bit here in North America, but it's still, basically, the engines are designed for whatever oils are already out there. They want the engines and oils to be as backwards and forwards compatible as possible. In Europe, specific oils are matched to specific engines.
But one thing that holds true for any engine, regardless of where it's made or how it's spec'd, and that is, each engine will wear differently every time you change oil brands or oil viscosities. Pick a good synthetic that's on the list of oils that the manufacturer recommends, and use it, or at the very least that brand, forever. Then, keep the oil clean by using a bypass filter, or changing out the filter once or twice between oil changes.
What's the best? Hard to say. As with many thing, people can be fiercely loyal about an oil. Not sure why, tho, since cold, hard numbers trump emotionally loyalty as far as an engine is concerned. The initial fill in mine was Mobile 1, 0W-40, and that's the only oil mentioned by name in the Technical Service Manual. That alone is enough to convince me, but I also looked at the results of studies and tests, and Mobile 1 really did come out on top with most categories. But really, any oil that the manufacturer recommends is fine. Just pick one, whichever one that's on the list that also blows yer skirt up, and use it forever. Don't be changin' oils to give it a treat or just to try something different - it's a machine, treat it like one. It wants the same thing every time all the time. That way it'll wear the same way all the time every time, and as the engine ages it won't have worn a bunch of different ways because of different oils. It's real easy, man.