Interesting discussion on an RS6 test drive...
 

Says the average fuel consumption is about 10 mpg!!!! Yikes - good thing I have another 7-8 months to save for gas money.<ul><li><a href="http://www.rs4.org/aspforums/Topic.asp?topic_id=2483&amp;forum_id=27&amp;Topic_ Title=RS6&amp;forum_title=Other+Audi+Cars">RS6 test drive</a></li></ul>

And another comparing the RS4 to the RS6 (times and such)
 

The happy RS4 owner has forgotten apparently that the RS6 is tiptronic and his faster RS4 is stick...