Where once manufacturers could boost their fleet average mpg by adding a couple of fuel-sippers to their lineup, now every vehicle must meet a government target.

WSJ: Henry Payne: The Motor City Roars Out of Washington's Shadow

Until now the only collaboration between VW and Porsche has been the Porsche Cayenne, which is a luxury version of the Touareg, a sport-utility vehicle made by VW. As the two companies get closer, Porsche's technology could boost the appeal of VW's more expensive models.

ECONOMIST: Volkswagen and Porsche