With the 2009 BMW 335d Sedan, it might seem the German automaker is taking a big risk with its reputation as the originator of the sports sedan by plopping a diesel engine under the hood.

To many Americans, diesel is the powerplant of plodding garbage trucks or the terrible 1980s GM car Uncle Earl owned. It’s an impression heavily seasoned with the words “noisy,” “smelly” and “dirty.” Sure, clean-diesel passenger cars are quiet, clean, and you’ll be hard pressed to smell even a whiff of exhaust. But what about speed?