While the corporate average for cars and trucks is 35.7 mpg and 28.6 mpg by 2015, BMW has to hit 37.7 mpg and 31.7 mpg, respectively. The reason for the disparity is the sliding scale the government used to account for differences in size in each automaker's lineup. Since BMW doesn't sell pickup trucks and it has plenty of small and midsize offerings, BMW has to hit higher fuel economy standards. What the CAFE numbers don't take into account is the fact that all BMWs are RWD, and there isn't a four cylinder engine to be found (in the U.S., yet). The Bush administration says its final fuel economy numbers will become public by the end of the year, and if companies like BMW don't get special dispensations, look for there to be smaller engines on the horizion, or bigger fines.
[Source: Automotive News - Sub. Req.]