BMW advocates for top tier gas...here is a source for who qualifies:
http://www.toptiergas.com/
Detergency has diminished relevance in direct injection engines, since the valves aren't treated to this attribute of fuel as in traditional fuel injection applications. All I need to do is take apart the intake manifold on my RS4 for this friendly reminder, the notorious carbon deposits are the Achillies heel of its otherwise amazing engine.