Iam just about to do an oil change before winter hits on my 1994 530i. From what i read it sounds like 0w40 is the best choice, iam just not sure if that applies for extreamly cold winters (it gets to -40 where iam), is 0w30 better for this kind of cold. I also have 12 liters of 5w50 (it was on sale) laying around, how would this be in the winter and the summer. If anybody has any other oil recomondations please let me know. thanks.