News & Features September 25, 2006, 1:52PM EST

2007 Mercedes-Benz E320 Bluetec

The only U.S.-market diesel passenger car meets new regulations for clean emissions and offers strong performance at a "bargain" price

by Gary Witzenburg

It's no secret that most Americans are less than fond of diesels. Past U.S.-market diesels have been clattery, smoky and painfully slow compared to gas-powered counterparts, and U.S. diesel fuel has been sticky, stinky, harder to find, and little (if any) cheaper than gasoline. Unless they've traveled to Europe lately, where quicker, quieter and nearly smokeless modern diesels have become more popular than gas burners due to their higher fuel economy and lower fuel taxes, they've had little reason to change that opinion. Until now.

Two important things are about to start changing it: First, 80 percent of U.S. diesel fuel by law will contain less than 15 parts per million of sulfur (vs. the previous 500 ppm), by this Oct. 15. Second, Mercedes-Benz will take advantage of this new ultra-low-sulfur fuel beginning the very next day by marketing a version of its 2007 mid-range 320 sedan powered by an all-new 208-hp 3.0-liter turbodiesel V-6 (replacing the previous in-line six) with "BLUETEC" exhaust-cleansing technology. M-B BLUETEC diesels will then spread to other markets and models, including a diesel Jeep Grand Cherokee and other Chrysler products.

Mercedes says this new E320 BLUETEC provides "outstanding driving dynamics, unprecedented efficiency and impressive environmental

compatibility." With its prodigious 388 lb-ft of torque, it offers owners the rare combination of V-8-like performance (zero to 60 mph in 6.6 seconds), four-cylinder economy and up to 700 miles of range - better on all counts than a similar-size gas V-6 - while showing little overt evidence of dieselness.

BLUETEC revealed

BLUETEC is a concept that Mercedes says will clean diesel emissions enough to meet more advanced diesel regulations taking effect for the 2007 model year. Including the Bluetec's catalytic converters, the system also uses particulate filters and a new system that treats nitrogen oxide emissions enough to meet the more stringent standards.

All this gets the '07 E320 BLUETEC into EPA's "BIN 8" emissions category, clean enough for 45 states in 2007 but not for California and those four pesky northeastern states that insist on emulating California's standards. The next step needed to satisfy their tougher "BIN 5"requirement (which will be the 50-state federal standard in 2009) will be an additional module involving injection of liquid urea, called AdBlue, into the process, reducing nitrogen oxide emissions another 80 percent. The AdBlue system will require regular fill-ups of fluid, likely to be done at the same time the car has an oil change.

The EPA is working with automakers to determine how to ensure that diesel owners do refill their urea tanks as needed - perhaps by mandating greatly reduced performance by the engine, or even preventing the engine from starting when the urea tank is empty. To our knowledge, M-B will be the only OEM offering (45-state) passenger car diesel engines in the U.S. until this issue is resolved.

The only diesel

Other than offering America's best (and, for a while, only) diesel passenger-car engine, the E-Class is modestly upgraded for 2007. Most significantly, it debuts M-B's first extensive use of lightweight aluminum body panels and chassis components in volume production, including the hood, front fenders, deck lid, front and rear subframes, and more.

The frontal look is mildly restyled, more aggressive, and more aerodynamic, while the interior gets a new steering wheel and shift lever and a nicely revised layout for the automatic climate control. The drag coefficient improves to 0.27 vs. the previous 0.29. New standard equipment includes a glass sunroof, a Harman/Kardon Logic 7 premium audio system with a six-disc CD changer and (for the wagon) a power liftgate. The rain-sensing wipers follow separate patterns to maximize the area cleared, their blades are hot-air heated when parked, and the washer fluid is electrically heated.

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