If I could get it easier I would use SUNOCO RACING 20W50, as I can't I would use Silkolene Pro S from Matt Lewis, though mobil 1 is also a great oil, it "earned" it's name from the bmw going non stop round the track only stopping for fuel and servicing, no wonder it did great as these are the ideal conditions with it never getting cold!!
When the engine is cold there is more blow by past the rings, this and the normal blow by contaminates the oil, that's the reason it goes black, ie carbon is black, giving your engine a good thrash once in a while helps the oil enormously, just ensure take it easy when cold, I don't use any boost until up to temp wherever I can help it.
tabetha