Calling your vehicle the "world's cleanest diesel" takes a lot of crust. Even so, Mercedes-Benz has a number of reasons for the claim. Its E320 BLUETEC luxury sedan has garnered honors since appearing on the scene as a 2007 model using the new ultra-low sulfur diesel fuel now mandated for the U.S.

Should long-ago memories of under performing, over polluting diesel autos remain, those are a world apart from the turbocharged E320 BLUETEC. A top sports sedan, with luxurious amenities, state-of-the-art electronics and no apologies performance credentials, this is the kind of aspirational vehicle potential buyers strive for. How it gets there is pure Mercedes.

The German auto company has restyled its E-Class vehicles for 2007, with a sporty new appearance including restyled front grille and headlamps, more aggressive front bumper and more aerodynamic side mirrors. Inside, a new shifter, steering wheel and automatic climate control layout are enhanced with four new interior colors. The harman/kardon Logic7 premium audio becomes standard. So does the glass sunroof, six-disc CD changer and power liftgate on wagon models. There's a system to channel rainwater away from the windshield for safety. And the ultra-smooth seven-speed automatic transmission has a Touch Shift when manual mode driving is preferred. The transmission improves performance while boosting fuel economy. With that as a base, the E320 BLUETEC had no place to go but up.

A major concern with diesels has long been how to eliminate two persistent problems: Smog-producing emissions gas, nitrous oxide (NOx), and particulates, those microscopic bits of grit that form clouds of black dust. Mercedes solved the problem by converting NOx into harmless nitrogen and filtering out and burning particulates, like the way a self-cleaning oven disposes of dirt.

Mercedes-Benz estimates best mileage at 27 city and 37 highway for their premium earth friendly sedan with the get-up-and-go of a V8 engine packed into a 3.0-liter, turbocharged V6.

At $52,325 (or $61,000 for an option-loaded version), it kicks in a scant $1,000 higher than standard gasoline powered E-320.