As with so many modern diesels, the E220 CDI blows old notions of turbo-diesel driveability out of the water. The sound quality is different from a gasoline engine's, but it's really only discernable during acceleration, not when cruising or at idle. The two-stage turbo is seamlessly integrated, so throttle response is predictably linear.
I drove an automatic, which was a five-speed (with a traditional shift lever on the console) rather than the seven-speed automatic (with electronic, column-mounted PRND selector) that Mercedes puts in our V-6 and V-8-powered E-class cars. Factory-measured acceleration is a brisk 8.3 seconds from 0 to 62 mph, and indeed the diesel steps out quickly off the line, thanks to an ultra-low (1400 rpm) torque peak. Mid-range acceleration is more leisurely than with our gasoline engines, but would be plenty for most drivers. High-speed cruising, though, is effortless. The only time the E220 CDI feels slow is when you try to drive it hard through tightly curving back roads; this is not a car that wants to charge from one apex to the next.
Overall, though, this 39-mpg E-class comes across as a very convincing executive conveyance that just happens to be more economical than even the smallest econobox. Should the dark days of $4 a gallon gasoline return - and who thinks they won't? - Mercedes, with this engine, or better yet, the just as economical but even more potent 369-lb-ft E250 CDI version, could blow Americans' minds by providing hybrid-like fuel economy and a luxury-car driving experience.