2010 Mercedes-Benz GL350 BlueTEC – Click above for high-res image gallery

Drop the term "Big Benz" in conversation and most people assume you're talking about the Mercedes-Benz S-Class. While the full-size flagship sedan has – deservedly – earned that moniker over the years, when it comes to sheer size and volume, the GL-Class is truly Benz' behemoth. But don't take that as a negative. The GL350 Bluetec, the automaker's diesel-powered variant of its seven-passenger full-size sport utility vehicle, has plenty going for it. Under the hood is a torque-laden, fuel-efficient diesel, and after a week pulling family duty, we emerged impressed. Find out why after the jump.

Photos copyright ©2010 Michael Harley / AOL

Today's Mercedes-Benz lineup seems to have the breadth to outmatch General Motors. The German automaker offers the C, E, S, CLK, CLS, CL, SLK, SL, SLR, R, GLK, GL, M, G and SLS models. Mixed throughout its alphabet soup are coupes, sedans, convertibles, sport utility vehicles and even supercars. There are also gasoline, diesel and hybrid powertrains. Distinguishing itself as the only seven-seat SUV and the largest non-commercial passenger vehicle offered by Mercedes-Benz is the GL-Class.

In North American guise, the GL is offered in three variants: The "entry-level" model, and the subject of this review, is the diesel-burning six-cylinder GL350 Bluetec. Positioned further up the food chain are the eight-cylinder GL450 and the even mightier GL550 – both of which drink gasoline at a prodigious rate, earning an EPA combined fuel economy figure of 14 mpg.

The appeal of the GL-Class is its roomy seven-passenger cabin, generous cargo capacity, truck-like ground clearance and ability to tow upwards of 7,500 pounds. Those uninterested in hauling weekend paraphernalia can get their paws on the "its-not-a-minivan" R-Class, which manages 2,500 pounds of towing and makes due with more passenger-friendly ground clearance. But what immediately impresses with the GL is its uncanny ability to hide its mass – it's often mistaken for its smaller (but still large) sibling, the five-passenger M-Class.

Visual illusions aside, the GL-Class is nearly as big as a Cadillac Escalade. Yet unlike GM's high-riding luxo-ute, Mercedes-Benz has engineered the GL-Class with unibody construction. In return, the European is 400 pounds lighter than the American and its entire platform is stiffer.

The chromed "350GL" insignia on the rear liftgate infers an engine displacement of 3.5 liters, but don't be fooled. Today's badging nomenclature often has very little to do with what's going on under the hood, and in the case of the GL350 Bluetec, it boasts a 3.0-liter (2,987 cc) all-aluminum six-cylinder turbodiesel fitted with an intercooler. The powerplant delivers 210 horsepower at 3,800 rpm and 400 pound-feet of torque starting as low as 1,600 rpm. The EPA rates the GL350 Bluetec at 17 mpg city, 23 mpg highway and 19 mpg combined. Mated to a standard seven-speed electronically-controlled automatic transmission, the 5,423-pound oil-burner will accelerate to 60 mph in just over eight seconds.

Unlike the archaic live axle suspension found under the rear of the Escalade, the GL-Class utilizes an independent double-wishbone in the front and a four-arm multilink in the rear. All four corners are also dampened by a standard air suspension system – dubbed AIRMATIC – and the SUV rides on 20-inch alloy wheels wearing wide 275/50R20 tires.

Now in its fourth year of production (originally launched as the GL320 in 2006), the GL350 Bluetec has received a minor makeover for the 2010 model year. The freshening included new bumpers, front and rear skid pates, chrome roof rails, LED daytime running lights and a bump in wheel size from 19 to 20 inches as standard equipment. The interiors were fitted with improved seats with active headrests, a new leather steering wheel, redesigned instruments and upgraded burl walnut trim.

Decorated in Boralo Red (read: burgundy) paint over Cashmere leather, our 2010 GL350 Bluetec tester arrived with a base price of $59,950. Several individual option packages, including an upgraded steering wheel, full leather and adaptive xenon lights bumped the price up a bit. However, the big hike came with the "Premium 2 Package" ($5,950) that includes navigation, COMAND voice control, Harman/Kardon LOGIC7 audio, HD Radio, an iPod interface and keyless ignition. When the adding tape stopped and destination/delivery was added, the grand total for GL350 Bluetec was $70,945.

Without question, the GL350 Bluetec is beautifully appointed. Passengers are greeted with yards of flawlessly sewn leather on the seats and doors, while darker contrasting leather covers the dashboard. Deep glossy wood trim is balanced with brushed aluminum accents on the vents, dials and various grab handles. The center console is large (thanks to the electronic P-R-N-D controls located up on the tree) and there's storage galore. Fit and finish is excellent, the quality of materials is superb and cabin lighting is nearly perfect. Distinctively European in execution, the overall aura of the cabin is classy, well-polished and appealing.

Better still, all seven seating positions are comfortable. The front seats are very supportive, especially for the lower back, feeling as good after 10 hours as they do after 10 minutes. Second-row passengers are equally as content as they enjoy generous room for knees, legs and feet. The third row is a very pleasant surprise. Many SUVs have the obligatory seats back there (BMW X5, Audi Q7, Acura MDX, etc...), but more often than not, they are nothing more than thinly-padded uprights bolted to a shallowly scalloped floor. Thanks to the ML's unibody platform, the German engineers were able to carve out a deep and accommodating passenger compartment in the "way back" of the GL. (By the tape, the last row in the big Mercedes offers as much leg room as the second row in a mid-size Audi A4 sedan). Making it even more pleasant, entry/egress is easy as the second-row seat pivots forward and completely out of the way. It says volumes about comfort when adults volunteer to sit back there for a 40-minute trip – and emerge with a smile.

Primary instrumentation, with large round dials set immediately behind the four-spoke steering wheel, is excellent. However, the sea of small square buttons bracketing each side of the 6.5-inch COMAND navigation and infotainent display require that the driver's eyes leave the road for several seconds to operate – a shame, as the navigation system is very good. However, it's worth noting that the graphics on the monitor are as crisp and clear as those on an iPhone.

We found quirkiness with the turn signal stalk on the left side of the steering wheel. Nearly every automaker places it at the horizontal nine o'clock position, while some manufacturers position it slightly higher up at ten o'clock position. Mercedes-Benz drops the stalk down to eight o'clock, and puts the cruise control up at ten o'clock. Those unfamiliar with the non-standard arrangement will likely find themselves repeatedly and inadvertently fumbling with the cruise control operations when simply trying to summon a few blinks to change lanes.

We also liked the color-coded phone icons (red to hang-up, green to dial), but found the numeric keypad that shares functions with the map display to be confusing and a quite a reach from the left seat. The HVAC temperature knobs were easy and intuitive, but the console-mounted radio volume knob was simply too shallow for our big fingers to comfortably grab – it has to be a bit taller – but thankfully there's a redundant control on the steering wheel.

The commanding view from the driver's seat offers excellent visibility of the conditions outside whether darting through traffic or cruising on the open highway. The GL's size, however, works against it when the speed slows to a crawl. It's a guessing game judging where the front wheels are, especially when parallel parking along a curb or attempting to maneuver around a small obstacle. Backing isn't any easier as the GL-Class has particularly undersized exterior mirrors. Our test model was fitted with a rear-view camera that helped remove most of the mystery – until it rained and the drop-laden lens refracted the world into a blurry underwater mess.

Outward appearances say the Mercedes-Benz GL350 Bluetec is going to drive like all of the other big SUVs. And as expected, it does. However, this seven-passenger German is actually enjoyable to pilot whether cruising down the highway or through a mountain canyon. It handles much lighter than its weight would suggest, thanks to its capable suspension and generous contact patch.

We put the GL-Class through its paces, and taking advantage of its passenger volume, we frequently had all three rows occupied with nary a complaint. At one point, we took the GL350 Bluetec on a one-day 200-mile jaunt across the L.A. Basin during a driving rainstorm. The automatic rain-sensing wipers kept the glass spotless while the automatic climate control ensured all windows, even with seven passengers on board, remained completely fog free. Like all GL models, ours had the standard all-wheel drive and four-wheel electronic traction system (a.k.a. "4MATIC") that's completely transparent in its operation. Inclement weather will not deter this SUV.

What sets this model apart from its GL-Class siblings is its superb diesel engine. Ignore the mediocre horsepower rating and take a look at the wonderful 400 lb-ft of torque. None of the eight-cylinder models can match it. The twisting power of an ox gives the Mercedes a quick jump off the line and a confident pull on the highway, even when passing on a grade. Sport utility vehicles are perfect candidates for turbodiesel engines, and the GL-Class is no exception.

As mentioned, the Feds slap the GL350 Bluetec with a combined fuel economy figure of 19 mpg. However, we saw 26 mpg during most of our highway cruising and our overall economy was in the low 20s the whole time. Most amazingly – and we are still shaking our heads in disbelief – the "lifetime economy" trip computer on our tester had never been reset, reading an even 22.0 mpg over the past 4,222 miles. An impressive feat for anything of this size and weight.

The biggest Mercedes SUV is one fine land yacht, but the competition in this well-to-do segment is fierce. In addition to the Cadillac Escalade, the stage is crowded with the Lexus LX570, Range Rover, Infiniti QX56, Audi Q7 and Lincoln Navigator. The Escalade vaunts its hybrid powertrain, while the Q7 offers a diesel. The QX56 from Japan points to its technology, while the traditionalists, both the LX570 and Range Rover, take pride in their off-road prowess. The Navigator, meanwhile, boasts luxury appointments and an industry-leading infotainment system.

Nevertheless, single category wins don't make champions among these captious rivals – front-runners need to deliver across the board. As perhaps the only SUV in the segment capable of balancing luxury appointments, driving dynamics and passenger capacity this well – all while delivering very impressive fuel efficiency – the 2010 Mercedes-Benz GL350 Bluetec remains unlikely to be ruffled by its challengers.

Photos copyright ©2010 Michael Harley / AOL

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