Every time a luxury green vehicle hits the market, it should remind us that going green does not need to leave us exiled to those Priuses, Insights, and Civics.

Such vehicles contribute to a lingering perception - and fear - among consumers that a green vehicle equals tofu, granola, and sunflower seeds. It doesn't help that some chauffeured transportation companies offer the Prius as a serious livery vehicle.

Well, move aside, Prius, you preening little egglet impostor of a chauffeured car. The Mercedes R320 is ready to sideswipe you off the autobahn of luxury.

I got a chance to feast on the Mercedes R320 last fall, as Mercedes rolled out a livery version for 2009. And it's definitely not roadway trail mix; driving the R320 is more like dining at a Ruth's Chris than some snotty little vegan joint next to a boutique. The R320 not only sunders the earthy stereotype of green vehicles, but it helps pull the reputation of diesel vehicles out of the truck stop as well.

The R320 qualifies as a cross-over SUV - the 21st century term for a station wagon all cross-dressed as a sport utility vehicle. Driving it reaffirms what Germans do so well with vehicles: Provide graceful, understated, sophisticated elegance backed by solid structures and refined precision. The R320 just feels safe and solid, with firm, black leather seats that relax. We may never find such solid simplicity in our baleful, bailout economy, but the R320 can provide it daily.

What makes the R320 so green is its combination of clean diesel engineering and even cleaner BlueTEC emissions technology. Mercedes has refined its emissions technology since releasing the first generation of BlueTEC in 2006. It now provides an additive-based second generation version just in time for some of its 2009 models. That should assuage some of the global warming hysteria that persists despite sub-zero winters.

But greenest of all on the Mercedes R320 is the double-retractable dual sunroofs that open over both the front and rear seats. You can simply pull back the interior roof panels, leaving a glassed-in view of the trees above. Nothing completes the green experience of clean diesel and low emissions more than a roofline view of passing flora and blue sky. For chauffeured clients, the balance of headroom, legroom, and lumbar support makes it easy to lean back and contemplate greener lifestyles.

As can be the case with German automotive engineering, the automakers often master the macro-areas of their vehicles, but then get a bit too micro in their meticulous attention to detail. The R320 has three irritating tics:

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Transmission control: What was Mercedes thinking? Instead of a thick-grip connected to the steering column, or the ubiquitous center console, Mercedes for some unfathomable reason has created a transmission shift via a narrow control stalk on the right side of the steering column. Think wiper blade control. During my first several days driving the R320, I was utterly befuddled on how to shift the gears via the control stalk and end push-button. What's worse, I would "pop" the vehicle into reverse every time I wanted to douse the windows with wiper fluid or use the blades, thinking the stalk was for the windshield wipers. After a few experiences like this, I was ready to break off the transmission sticklet and toss it out the power window.

Fortunately, the transmission shift is set up to be moron-proof. Every time I tried to wet the windshield, a readout on the dashboard told me I could not shift in reverse. Thank goodness, since without such a protective feature, I likely would have left a trail of broken transmission parts as the car skidded to a grinding halt.

• Lesson for automakers: Never design a transmission control that you can shift with your pinky in the air.

Manual gear shift: To create the illusion of joyful stick shifting, many automatic transmissions now come with a manual, clutchless shift feature. VW refers to it as, "Tiptronic." Here again, this was impossible on the itty-bitty transmission sticklet. So Mercedes installs two stubby, "guitar piks" on either side of the steering wheel that you can click with your thumbs. Any driver in a logical frame of mind would conclude these are volume controls for the sound system, so they don't have to look down at the stereo to adjust volume. After a few clicks to turn down the volume, the R320 would lurch and the engine would hum louder as it downshifted. At first, I had to pull over to the side of the road as I was in first gear and couldn't quite figure out how to get out of it.

• Lesson for automakers: Be logical and do no harm. You shouldn't need an owner's manual to figure out gear shifting.

Acceleration/gas pedal: To tap the real power of the R320, you need to depress the gas pedal almost halfway down. In most cars, such mashing would get you a tire-squealing, jack-rabbit forward lunge. A Mercedes rep explained to me that Mercedes designs the accelerator as such for safety reasons. If you want the power, you really have to step in it. That way, a reflexive foot tap or toe spasm won't send the car rocketing forward. I disagree. With the accelerator, your foot should be the master, not the pedal. So when you want the power, you should be able to command it right away.

Finally, I had one last hang-up about the R320, and like the above quibble list, it's not a make or break issue: That diesel sound. I admit it traumatizes me, since I often drove an '80s era VW Rabbit Diesel in high school that went from 0 to 60 in 17.4 seconds. What's more, the Rabbit felt and sounded like an 18-wheeler, with its growling, guttural, machine-gun like roar. Residents in my suburban neighborhood would always turn heads toward the diesel cacophony, which to them sounded more like Detroit on Halloween night or Beirut convulsing into a Hezbollah hissy fit.

Fortunately, Mercedes has progressed admirably toward a quieter, diesel engine, but it still has that sound when idling. Overall, the R320 meets the clean, green demands of chauffeured luxury transportation, although operators should make sure they adequately train the chauffeurs on the transmissionette.

Even with its subdued diesel acoustics, the Mercedes R320 BlueTEC is certainly much more credible as a chauffeured green vehicle than that quiet, mousy Prius.

What is BlueTEC?

BlueTEC, which has been proving its worth in the truck and bus segment since 2005, is featured in the new GL-, ML-, and R-Class Mercedes models launched in the U.S. in late 2008. Here, an additive known as AdBlue is injected into the exhaust gas flow in order to release ammonia, which reacts with nitrogen oxides in the downstream SCR catalytic converter to form harmless nitrogen and water. This second BlueTEC version is thus even more effective than the first generation, and the vehicles that use it not only meet the stringent Bin 5 standard but also have the potential to achieve emission levels below the limits stipulated by the future Euro 5 and Euro 6 standards. BlueTEC runs cleanly enough to meet the strict emission standards of every state including California. A seven-speed automatic transmission and a BlueTEC/AdBlue diesel drivetrain can achieve a 25% reduction in fuel usage compared to a 4.6-liter V8 gasoline engine version. Source: Daimler and Mercedes.

Mercedes R320 Facts
MSRP: $47,950
Engine: 3.0L V6
Horsepower: 210 hp @ 3,800 rpm
Transmission: 7-speed automatic
EPA mileage: 18 mpg/24 mpg
Fuel tank: 21.1 gallons
Range: About 500 to 600 miles
Vehicle weight: About 5,100 pounds
Wheelbase: 126.6 inches
Length: 203 inches
Width: 85.4 inches
Height: 65.4 inches
Cargo capacity: 42.2 cubic feet
Carbon footprint: 10.6 annual tons of CO2
Annual fuel consumption: 827.4 gallons per year @15,000 mi.
EPA pollution score: 6 out of 10

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