Mercedes-Benz calls its R-Class vehicle a “sports tourer,” but with its three rows of paired seats, high roofline, and large load capacity, we have a different description. We just call it a station wagon. The MSRP is $49,150, with a tax credit of $1,800 tax credit to support “advanced lean-burn vehicles.”

Introduced for the 2006 model year, the R-Class is by far the least successful of the three related Mercedes-Benz large sport-utilities built on the same line in Alabama. Let’s compare the three:

  • The five-seat Mercedes ML320 Bluetec is the clean-diesel-powered suburban Mom machine that competes against the BMW X5.
  • The big, boxy, seven-seat GL, available as a clean diesel with the Mercedes GL320 Bluetec, is the brawniest and blingiest of the three. It goes up against the Cadillac Escalade.
  • What’s the competition for the R-Class? Uh…maybe Benz’s own midsize E350 station wagon.

Nonetheless, for 2009, the company is offering the R-Class with a new 210-horsepower, 3.0-liter turbocharged, direct-injection V6 diesel. The R320 BlueTec diesel, rated by the EPA at 18 mpg city / 24 mpg highway, costs $1,500 more than the gas-powered 3.5-liter V6.

BlueTec Means Green, in German

In 1936, Mercedes-Benz was the first carmaker ever to offer a passenger car with a diesel engine. Since then, its legendary and durable diesels have been a point of distinction for the marque. Mercedes-Benz continues to offer diesels in several US vehicles despite this country’s stringent emissions standards, which have required it to develop entirely new technologies to make them clean enough to sell in all 50 states.

The new 3.0-liter turbodiesel uses the Mercedes-Benz “BlueTec” pollution control system, which includes particulate filters and two catalytic converters. A new element is liquid urea, injected into the exhaust stream, to make the chemistry come out right for lowering nitrous oxide emissions. Along with particulates and soot, they’re the Achille’s Heel of modern diesel engines.

The R320 BlueTec is a full 203 inches long, and opinions of its styling have—to be charitable—varied considerably. We rather like it, but then we’re big fans of the old-fashioned station wagon anyhow. Some have called the R-Class a “minivan,” but we have to disagree with that. No sliding doors!

The mileage ratings (18 mpg city / 24 mpg highway) are better than the 15 mpg city / 19 mpg highway of the R350 gasoline version. And as usual, remember that sometimes diesels deliver higher mileage in real-world usage than their ratings would indicate.

Spacious but Ponderous

The R320 BlueTec goes from 0 to 60 mph in 8.6 seconds, tolerable for a 4,940-pound vehicle that seats six but certainly far from the front of the pack. Reviewers have complained that it’s far from sporty, and feels consistently heavy, even ponderous for such a relatively low car.

Befitting a Mercedes-Benz, the long and lavish option list lets owners deck out their cars with a variety of entertainment and comfort features. In particular, the $8,000 “Premium Package 2” adds a rear-view camera and parking sensors, three-zone climate control, and a jaw-dropping Harmon-Kardon surround-sound system. More money buys you keyless entry and ignition, a rear-seat entertainment package that includes rear-seat LCD screens and a second-row DVD player, and even a panoramic sunroof to prevent third-row riders from feeling closed in.

Mechanically, the R320 BlueTec uses the company’s well-regarded 7-speed automatic, mated to standard 4Matic all-wheel-drive. The optional Airmatic suspension gets high marks for comfort. The car also includes the Mercedes-Benz Pre-Safe system, which anticipates accidents and pre-loads the brakes and seatbelts, among other safety features.

Adding AdBlue

The “AdBlue” liquid urea solution is held in its own tank, which must be refilled every 10,000 to 12,000 miles. To comply with EPA mandates that a vehicle’s emissions system must work properly for 8 years or 100,000 miles without any owner intervention or maintenance, Benz includes AdBlue refills in mandatory dealer service intervals.

What happens if the owner runs late, or the car runs low? After a series of warnings, the BlueTec diesel simply refuses to start if its emissions system doesn’t have enough AdBlue, meaning the car must travel back to the dealer via flatbed truck.