The 2010 GL-Class has been lightly restyled with new bumpers, lighting front and rear, wheels and front skidplate.Cabins have been similarly updated for the 2010 model year while maintaining familiarity with Mercedes' line and the GL in particular.The diesel model has been rebadged GL350 BlueTEC (from GL320 BlueTEC) though the engine remains a 3.0-liter.The 2010 GL350 and GL450 come standard with run-flat tires.

All GL models come with a seven-speed automatic and 4MATIC full-time all-wheel drive that distributes drive to both axles equally, and all employ air suspension for good ride comfort on a variety of surfaces and level attitude regardless of load.A full suite of safety equipment is standard across the board.

While their names sound similar, don't confuse the GL-Class with the venerable G-Class or Gelandewagen meant for more severe off-highway travel.The GL shares nothing in common with the utilitarian G-Class beyond the 550's engine and the automatic transmission.The GL-Class shares its basic platform with the ML-Class and R-Class.

The Mercedes-Benz GL-Class is large and surprisingly capable off road yet feels reasonably car-like on the road.That car-like feeling comes in part because it is built around a unibody architecture instead of traditional body-on-frame construction (as the G-Class uses).Mercedes says a GL-plus-driver is strong enough to tow a 7500-pound trailer, but verify tongue weights and ratings before making decisions.

Primary competitors include the Audi Q7 and BMW X5 which both offer a diesel engine option, as well as the Cadillac Escalade, Infiniti QX56, Lexus GX460 and the Land Rover LR4.Especially for those interested in carrying adult-sized persons in the third row seat, the GL-Class offers a compelling argument of efficiency, space and features.

GL350 BlueTEC 4MATIC ($59,950) and GL450 4MATIC ($60,950) are similarly equipped, with MB-Tex faux leather upholstery, dual-zone climate co troll, power driver's seat, heated power mirrors, heated windshield washer system, reading lamps, burl walnut trim, first-row moonroof, third-row panorama roof, rain-sensing wipers, HomeLink, cruise control, six power windows, and trip computer.

Options include leather upholstery, three-zone climate control, tow hitch, wood/leather or heated steering wheel, heated/ventilated front seats, Parktronic proximity sensors, running boards, lighting package (adaptive bi-Xenon headlamps with heated washers), dual-screen DVD rear entertainment system, LED daytime running lights), illuminated door sills, roof rails and metallic paint.Premium package 1 includes COMAND/voice recognition HDD navigation with Zagat guide, HD and Sirius radio, and personal electronic inputs, power folding mirrors, power tilt/telescope steering column and driver memory, power liftgate, 115v outlet, and auto-dimming mirrors, while premium 2 adds a harman/kardon Logic 7 sound system and Keyless go.Dealer accessories run gamut from child seats and roof racks to SD memory cards though they can be pricey (a 2GB card listed for $48 the same day an 8GB card could be purchased for $38 at retail stores).

The GL550 4MATIC ($82,850) comes with many above options as standard, including full leather, Parktronic, rear-view camera, premium audio, adaptive bi-xenon headlamps, infrared-reflective glass, metallic paint, Adaptive Damping Suspension and Keyless Go.Options are limited to a chrome package, roof cross bars, trailer hitch, rear entertainment system, heated steering wheel (no charge) and rear seats, illuminated door sills, and an upgrade to Nappa leather upholstery.

Safety features that come standard include eight airbags, including side airbags for all four outboard first and second-row seating positions as well as side curtain airbags that protect occupants in all three rows.GL models come with active front head restraints, LATCH tethers for child safety seats, adjustable headrests and three-point safety belts for all seating positions; make sure everyone in the vehicle always wears those seat belts because they're your first line of defense in a crash.Active safety features (to help you avoid a crash) include an Electronic Stability Program, anti-lock brakes with Brake Assist Plus, and four-wheel electronic traction control.Optional safety features include Parktronic and a rear-view camera, each of which can help alert the driver of obstacles or people, including children, behind the vehicle.The last time we checked, the GL-Class did not come with child locks on the rear side doors.

Added in 2009, Pre-Safe is a system which can sense an impending collision by myriad input factors.Introduced previously on the Mercedes-Benz S-Class sedans, Pre-Safe automatically tightens the front seat belts and moves the front passenger seat to a position that can provide better protection.Side windows close to provide better support for the curtain air bags.If the system senses an impending rollover, the sunroof also closes.

Unique to the GL550 is a deeper, more aggressive front-end treatment, including a larger three-bar grille and the logo star is the largest of any North American Mercedes.With its 21-inch wheels, fat tires and dual-split exhaust outlets the 550 is the most imposing GL.

Seen in profile, the nicely raked windshield and bulging wheel arches over large wheels (19-inch or better) help balance what is basically a tall and long vehicle.Although tall and long, the slightly narrower GL doesn't look as bulky as, say, the Chevy Tahoe and GMC Yukon.And even with the squared-off rear edge of its D-pillar, the GL doesn't look as boxy as the Jeep Commander or Mercedes' own G-Class.

Viewed from the rear, the GL offers a formidable stance.It's tall and wide, with a large rear hatch opening and large LED tail lights, all sitting above a substantial skid plate bracketed on either side by large, rectangular exhaust pipes.

Compared to the ML, the GL is over a foot longer overall and an inch wider in track (the left-to-right distance between the centers of the tires), though it is barely a hair wider overall and not quite an inch taller.Despite their similar styling, the Mercedes SUVs share only their front doors; otherwise, each has unique sheet metal.

As large as the GL may appear, it's three inches shorter than the R-Class touring wagon, which also has three rows of seating, though with less room for six occupants.

The GL is built using unibody construction rather than the body-on-frame design that full-size pickups and SUV's traditionally use.Mercedes notes that because of this architecture, the GL-Class is 300-600 pounds lighter than its full-size competitors.To make sure the GL class is strong enough, 60 percent of the vehicle structure is made from special high-strength steel.

An upright rear end minimizes snow accumulation and benefits cargo space.With all seats in their upright position, there's still 14 cubic feet of storage between the third-row seatbacks and the closed rear hatch door.A power folding feature for the third row is standard equipment on the GL with controls near the rear hatch and next to the right-side second-row passenger's seat.Power down those third-row seats, and cargo capacity expands to 43.8 cubic feet.Fold down the 60/40-split second row seats and the GL provides as much as 83.3 cubic feet for cargo.There's also room under the cargo floor for a full-size spare tire.

The interior layout is familiar to Mercedes drivers, with faux MB-Tex or real leather trim for the seats (Mercedes notes that not all luxury car buyers want leather seating surfaces), wood trim and metal rings around gauges, air vents, and cup holders.Switchgear is comprehensive without being overwhelming, and the shift lever on the steering column and paddles on the wheel allow for maximum console space.

The second-row seats provide ample room, with more head and legroom than a Cadillac Escalade or Chevrolet Suburban; the door opening is substantial so shoes and long legs don't get caught on the pillar.When occupied by only two people, the back of the center section can be folded down as an armrest and storage tray.

We climbed into the third row and found room for two six-foot adults to ride back there, each in a separate seat; again with more headroom and nearly eight inches more legroom than the Escalade, and just half an inch less legroom than the much longer Suburban.The room is enhanced by foot wells for your feet so you don't sit with your knees at chest level, and even the third-row seats are thickly padded to provide comfort.Fears of claustrophobia back there evaporate quickly thanks to the sunroof that extends over the third row and opening quarter windows.

The COMAND system features a 6.5-inch color display screen; a standard in-dash, six-disc DVD / CD changer; and a Bluetooth interface that allows a phone still in a pocket or purse to be operated through the car's audio system.COMAND can also be equipped with an optional iPod/MP3 interface, Sirius satellite radio, HD radio, and an enhanced voice control system.It can play tracks stored on a data CD, DVD or SD memory card.The new system can also display maps and directions for the optional hard-drive navigation system, which can be set up for SIRIUS real-time traffic info and Zagat restaurant ratings as well.

All GL-Class models can be equipped with an optional 610-watt digital harmon/kardon Logic7 audio system, and a rear-seat entertainment system that includes two eight-inch screens mounted in the rear of the front-seat headrests wireless headphones and an integrated DVD player with dual-source capability.If you're in the habit of throwing your right arm behind the passenger seat when backing up, watch your rings don't scratch the screen.

Factory estimates say the flagship GL550 can accelerate from 0 to 60 mph in 6.4 seconds.The 382-hp V8, with four valves per cylinder, generates 391 lb-ft of torque from 2800-4800 rpm with all the smoothness you'd expect in a flagship.It also generates EPA ratings of 12/17 mpg.

The GL450, which is $21,000 less because it doesn't include as many standards, is more than adequate with its 335-hp (339 lb-ft; EPA 13/17) 4.6-liter V8 if towing or speed contests aren't on your agenda; Mercedes says only a half-second longer than the GL550 (and their estimates are conservative).Apart from the 21-inch wheels and more aggressive bodywork, a lesser GL can be optioned to match a GL550 in features.Indeed, for poor road areas, severe winter climes that frequently require snow chains, or those inclined to use the low-range gear in the Off-Road package, the GL450, with its standard 19-inch wheels, or GL350, are better choices.

For $1000 less than the GL450 you can get the renamed GL350 BlueTEC turbodiesel.While this 3-liter V6 delivers 210 hp it also brings 400 lb-ft of torque from 1600 rpm upwards, and torque is more important for most heavy SUV driving; though any combustion engine is affected by altitude the turbodiesel will lose a smaller percentage of its power as elevation rises.The GL350 will take about two seconds longer to reach 60 mph, which it does right in line with most 7-seat hybrid SUV's; diesels don't snap your neck from a standing start but once clear the crosswalk accelerate with more than adequate verve.The GL350 is also clean (the exhaust cleaner than ambient air in smoggy areas) and delivers EPA ratings of 17/23; our test drives have found EPA diesel ratings a bit pessimistic as we averaged better than 24 in myriad conditions.Every GL-Class may be equipped to tow 7500 pounds, giving the high-mileage diesel a substantial advantage over hybrids in this respect. A seven-speed automatic transmission is standard on all GL models and operates seamlessly as an automatic, or shift it yourself with paddles on the steering wheel.

The four-wheel-drive system, called 4MATIC, uses open front, center and rear differentials.Quite sophisticated, 4MATIC is designed to maintain mobility even when only wheel has traction by electronic intervention; this system should not be confused with the genuine locking differentials of the G-Class which deliver the utmost in traction.In normal driving, the system distributes power equally to front and rear wheels.The system includes DSR, a sort of low-speed cruise control for regulating downhill speed, and Hill-Start Assist, which keeps the GL from rolling backward when launched after being stopped on an uphill slope.4MATIC also adjusts anti-lock brake controls to provide quicker stops on slippery and unpaved surfaces, an important benefit many vehicles with ABS do not offer.

Airmatic is an air suspension system that uses air bladders instead of coil springs to adjust ride height by as much as three inches, and with the GL550's adaptive damping the driver can select from comfort and more aggressively sporty settings.The system automatically lowers the vehicle to enhance handling and aerodynamic efficiency at speeds of 77 mph or higher, and it levels the car regardless of load for stable handling, towing and visibility.

We did our driving on freeways, back roads, fire roads, and those marked for off-highway vehicles.Steering feedback was consistent, brakes (14.7-inches in diameter on the front wheels and 13.0 inches on the rear) were responsive and consistently predictable and the GL offered nice balanced dynamic capabilities when hustled through the curves on the narrow, hilly roads that wind through the vine-covered hillsides.The 550's fat 21-inch tires contribute commendable grip, and like the majority of wide, low-profile tires, follow pavement grooves, give sharper impact sensations, have notably higher replacement costs and can not use tire chains.

Correspondent G.R.Whale tested the GL550 in Idaho and the GL320 and GL450 in Los Angeles, with Larry Edsall reporting from Napa Valley.