Read Joe Lorio's comments on driving the 2008 Mercedes-Benz E320 Bluetec.
A very nice powertrain made all the better by its pleasant surroundings in the E-class. True, no one will mistake the Bluetec for a gasoline engine at idle, where it clatters like, well, a diesel. It's the same story when accelerating, but the engine is essentially silent when cruising. Speaking of accelerating, the thrust is considerable. And I saw an indicated fuel economy as high as 30 mpg on the highway.