The right lane of Interstate 5 in California's Central Valley is 350 miles of tortured pavement, continuously assaulted by heavy trucks driving between Sacramento and Los Angeles. Our Car Tech staff, bound for the Los Angeles Auto Show, barely noticed the deteriorated condition of the roadway as the soft suspension of the 2012 Mercedes-Benz ML350 Bluetec absorbed every knock and jolt. Mercedes-Benz may make forays into sport-oriented cars with its AMG division, but the ML350 Bluetec exemplifies what the company does best: luxury. Although not quite the uberluxury of a Bentley or a Rolls-Royce, it is still one of the most comfortable SUVs around. The cabin of the ML350 Bluetec is trimmed in thick leather and solid wood accents, and not all the buttons are plastic. In good ergonomic fashion, Mercedes-Benz puts the power seat switches on the door, along with memory buttons for saving a seating position. A lever below the steering wheel power-adjusts its tilt and telescoping, and all the windows go up or down at a single touch of their switches. The wheel turns with ease, power-boosted to make steering at low speeds effortless.

The right lane of Interstate 5 in California's Central Valley is 350 miles of tortured pavement, continuously assaulted by heavy trucks driving between Sacramento and Los Angeles. Our Car Tech staff, bound for the Los Angeles Auto Show, barely noticed the deteriorated condition of the roadway as the soft suspension of the 2012 Mercedes-Benz ML350 Bluetec absorbed every knock and jolt. Mercedes-Benz may make forays into sport-oriented cars with its AMG division, but the ML350 Bluetec exemplifies what the company does best: luxury. Although not quite the uberluxury of a Bentley or a Rolls-Royce, it is still one of the most comfortable SUVs around. The cabin of the ML350 Bluetec is trimmed in thick leather and solid wood accents, and not all the buttons are plastic. In good ergonomic fashion, Mercedes-Benz puts the power seat switches on the door, along with memory buttons for saving a seating position. A lever below the steering wheel power-adjusts its tilt and telescoping, and all the windows go up or down at a single touch of their switches. The wheel turns with ease, power-boosted to make steering at low speeds effortless.

The luxury driving character does not just extend to the soft suspension; exterior sound is also well damped out. During the hours spent driving down to Los Angeles and back, there was little discomfort. At the end of each stretch, we felt as refreshed as we had before setting out. The ML350's diesel engine generates plenty of torque, useful for getting heavy vehicles moving. Bluetec means our ML350 ran on diesel, which has its own set of pros and cons for a passenger vehicle. The turbocharged 3-liter V-6 engine had plenty of power, 240 horsepower and 455 pound-feet of torque by the numbers, to move this heavy SUV with ease. Whether charging onto the freeway from an onramp or pushing up over the Tejon Pass on the way to Los Angeles, the ML350 Bluetec never felt like it was wheezing. Diesel engines also generally get better fuel economy than gas engines, and the ML350 Bluetec is rated at 20 mpg city and 27 mpg highway.

Those numbers may not look dramatic, but they translate to 3 to 5 mpg better than the gasoline-powered ML350. On our trip, which mostly consisted of freeway driving, we came in at 25.8 mpg. Mercedes-Benz also fits the ML350 Bluetec with a 24.6-gallon tank, which gives it excellent range. On arriving in Los Angeles from San Francisco, we still had a third of a tank, which let us take a considerable chunk out of the drive back before a refuel stop. 4.55 a gallon when we filled up, that was also one expensive stop. The downside of diesel is it can be more expensive than gasoline, about 50 cents more per gallon in California. And the emissions system is more complex. Mercedes-Benz uses a system called AdBlue to clean up the ML350 Bluetec's emissions and comply with U.S. That 7-gallon tank needs to be refilled about every 15,000 miles. In diesel or gasoline form, the ML350 comes with a seven-speed automatic, the upper gears helping to keep freeway fuel economy high.

In current Mercedes-Benz fashion, the shifter is a small stalk on the steering column, and more appropriately called a drive selector, as it can only put the car in Drive, Reverse, Park, and Neutral. Our ML350 Bluetec also came with paddles on the steering wheel for manual shifting, but we only found use for them on steep descents, letting the engine do some of the braking. The cabin of the ML350 Bluetec embodies the luxury for which Mercedes-Benz has become known. The first letter of SUV means "sport," but the ML350 Bluetec did not exhibit anything like the cornering performance available from a Porsche Cayenne or even an Acura MDX. During turns, its soft suspension delivered a loose, floaty feeling, suggesting cautious speeds. However, the ML350 Bluetec can be optioned with an adaptive air suspension, which might make it more capable. The ML350 Bluetec comes standard with all-wheel drive, which will help its grip in slippery conditions, but don't expect serious off-road chops. There is no differential locking or even descent control, not that most buyers of this vehicle would end up in places where these features would be useful.

Very useful for our Los Angeles road trip, however, was the navigation system, which, as in most new Mercedes-Benz models, has high-resolution maps stored on a hard drive. The 3D-rendered buildings made maneuvering through the urban canyons of downtown Los Angeles easier. But on the freeway, the map insisted on displaying each exit, even ones that were not on our route, which became annoying. The navigation system's maps show in good resolution, and include rendered 3D buildings in some urban areas. This navigation system includes dynamic traffic routing, a definite plus when driving through Los Angeles. Having it set to confirm each route change was a mistake, however, as the heavy and constantly changing traffic conditions meant a dialog box asking for confirmation every couple of minutes. But this traffic avoidance feature obviously worked well, as we only experienced one section, only about a mile long, of slow traffic while driving into Los Angeles on a late Tuesday afternoon.