Mercedes-Benz beat BMW’s hydrogen-powered 7 Series and the Volkswagen Polo BlueMotion for top honors as the 2007 Green Car of the Year. We understand the choice over the BMW, which is just now becoming available in extremely limited quantities and for which a fueling infrastructure does not exist. But how could the E320 Bluetec beat the Polo, a fun-to-drive econo-hatch that gets about 60 mpg from its 1.4-liter TDI diesel engine? Our guess is that since the Polo isn’t sold in the U.S., self-important American jurors pooh-poohed the notion of giving Volkswagen the award.