2007 Mercedes-Benz E320 Bluetec & Vision GL320 Bluetec Concept

What's Special About It?
American buyers like the current Mercedes-Benz E320 CDI. It's the only diesel-powered luxury car sold in the U.S., and it has the highest fuel economy rating in its class (27 city/37 highway). But Mercedes can't sell it in the two biggest markets, California and New York, because it doesn't meet emissions standards and that's a problem.

Enter the 2007 Mercedes-Benz C320 Bluetec, an E-Class sedan powered by the cleanest-burning diesel engine in the world. Clean enough to certify it in all 50 U.S. states.

It starts with a completely different engine than in the existing E320 CDI, a 3.2-liter V6 instead of an inline six. Rated for 211 horsepower and an impressive 398 pound-feet of torque, this 24-valve, direct-injection V6 is fitted with piezoelectric injectors that allow for more precise fuel spray into the combustion chambers, and a turbocharger with a variable-nozzle turbine, basically a set of adjustable vanes that directs the recirculation of exhaust gases. There's also a particulate filter to reduce the amount of soot that comes out of the car's tailpipe.

However, what really makes the difference on the E320 Bluetec is its DeNOx storage catalytic converter. As its name suggests, it cuts down on the nitrogen-oxide emissions that have kept earlier diesels from 50-states certification.

But Mercedes says there's a way to remove even more nitrogen oxide from tailpipe emissions. It's called AdBlue, and the Vision GL320 Bluetec concept is the company's test subject. This diesel SUV has an onboard tank carrying an aqueous urea solution. Injecting the solution into exhaust gas releases ammonia (NH₃), and the ammonia reacts with the nitrogen oxide to form harmless nitrogen and water in a downstream catalytic converter.

If there's a disadvantage to AdBlue, it's that the 6.8-gallon tank must be refilled periodically. "As a customer, you can't do it yourself," says Matthias Flach, an engineer in Mercedes' Advanced Development department, but service technicians can easily top it off when the vehicle goes in for scheduled maintenance. "You only need 0.6 gallon per 1,000 miles," he adds.

The 2007 Mercedes-Benz E320 Bluetec will come to the U.S. this fall — before any other market in the world. And DCX CEO Dieter Zetsche promises it will be followed by production Bluetec variants of the GL-, M- and R-Class and the Jeep Grand Cherokee.

What's Edmunds' Take?
This is the beginning of diesel mania. Once Californians and New Yawkers get a taste of a torquey clean-burning diesel they won't look back. — Erin Riches