I typically use Total Energy 9000 5w40. we stock this at the shop and it far exceeds what BMW, Mercedes, and Porsche require. I like it for the "no sludge" that I have seen over the years.
Mobil 1 10-40 wt for me. Seems to perform well year around here in North Texas where 100+ degree days are common in the summer. Walmart stocks it, so that is a plus, too.
i bought my 2004 318ti new have always used 0w-40 mobil 1 but i change it at half bmw ,s service interval its now done 108k miles uses no oil at all have only changed the timing chain tensioner as recomened by bmw.Still has no oil leaks !!!! Runs as well as the day i bought it.