Mercedes-Benz has long been one of the greatest proponents -- and often one of the few proponents -- of diesel engines in U.S. passenger cars. With the recent increase in diesel offerings and renewed consumer interest in diesels in the United States, Mercedes has made a bold move, switching its mainstay E-class diesel from a V-6 to a four-cylinder. The result is eye-popping fuel economy married with surprising drivability.

In place of last year's 3.0-liter V-6 turbodiesel, the 2014 Mercedes-Benz E250 Bluetec uses a 2.1-liter four-cylinder. Despite its much smaller displacement, output is down by only 15 hp and 31 lb-ft of torque, with totals of 195 horsepower and 369 pound-feet. Even so, performance, predictably, is down -- the factory 0-60 time is now 7.9 seconds, versus 6.7 seconds for the E350 Bluetec.

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On the flip side, fuel economy has taken a big jump. Whereas the six-cylinder diesel recorded EPA numbers of 22/32 mpg, the new four-cylinder rings in with 28 mpg city and 42 mpg highway.

To further enhance the diesel's appeal and broaden its market, Mercedes now makes it available with 4Matic all-wheel drive. (With 4Matic, the EPA ratings are 27/38 mpg.) The company estimates that half of all E250 Bluetecs will be so equipped.

In a week's driving of a 2014 Mercedes-Benz E250 4Matic, I was able to beat both EPA figures. From Monday through Friday, I averaged 35 mpg in mostly suburban driving but with one foray into Manhattan. On the weekend, I took a trip up into the Adirondacks. On the nearly all-highway drive home, I got an indicated 44 mpg over some 250 miles. One wonders what that figure might have been if I'd been going the speed limit.

Keeping up with the fastest movers on the Northway was no problem for the 2014 Mercedes-Benz E250 Bluetec. The engine's meaty torque figure means a little extra shove is always readily available. Even around town, the E250 feels surprisingly quick in normal driving. Mercedes' always-excellent 7-speed automatic has low first and second gears that help the E250 step smartly off the line. And the turbo boost is perfectly integrated, making throttle response nicely linear.

So, given its impressively livability, and fuel economy that bests the gasoline E350 by 7 to 8 mpg (city) or 10 to 12 mpg (highway), is the Bluetec worth the extra cost? It might be, if there were an extra cost. In fact, the 2014 Mercedes-Benz E250 Bluetec is the least expensive E-class model. The rear-wheel-drive E250 Bluetec starts at $52,325, which is $500 less than an E350. The 2014 Mercedes-Benz E250 also undercuts the (six-cylinder) diesel versions of the Audi A6 and BMW 5-Series.

We'd say, then, that slipping a four-cylinder diesel into the E-class was not just a bold move but a smart move. Once again, with the 2014 E250 Bluetec, we find Mercedes-Benz doing its part to make diesel passenger cars more popular in America.