When designing the GL-Class full-size luxury SUV, Mercedes-Benz knew that covering the “basics” (room, luxury, power, safety, towing ability) would be the easy part. It was making the GL ride and drive with the agility and driving enjoyment of a good sedan that took the hard work.

There are certain elements that can’t be compromised when it comes to full-size luxury SUVs. One is room for seven in three comfortable seat rows. Another is a cavernous cargo area with the seats folded. The utmost in family safety and onboard entertainment options are givens, too. Having a 7,500-pound towing capacity is certainly on the wish list. Finally, you’ve got to have the power to do all that.

The 2010 Mercedes-Benz GL covers all those bases and more, starting at $58,200 for the GL320 BlueTEC. It’s when you drive the Mercedes GL that your eyebrows will rise. If you have not driven a GL, then you need to prepare yourself, first by forgetting that a big SUV has to handle like a big SUV. It’s in no way an exaggeration to say that the GL drives more like a well-mannered luxury sedan than a full-capability SUV.

That makes the GL a major departure from every other full-size luxury SUV on the market. First, there is nothing underneath the GL’s stylish, yet practical body to even suggest a kinship with pickup trucks. The GL’s super-strong unit body construction and four-wheel independent air suspension (with self-leveling) smooth out bumps far better than SUVs still clinging to “solid axle” rear suspension. Because the rear suspension is independent instead of a solid axle, the GL also provides more third-seat legroom.

The net result of this blend of car-like construction with SUV ruggedness is that the GL is not afraid of the curves or bumps that can, quite literally, shake up other big SUVs. Nobody is going to call the GL a sportscar, of course, but the GL’s agility may have you glancing in the rearview mirror to remind you that this is a three-row utility vehicle, not a sedan.

The GL gives you three power choices for 2010. Let’s start with the GL320 BlueTEC because it has some numbers that may shock you. Fuel efficiency is rated at 17 mpg city and 23 mpg highway. That’s on a par with some midsize luxury sedans. The reason? The 3.0-liter clean-diesel V6 that delivers a mammoth 400 lb/ft of torque. It’s super-quiet, responsive and, as you’ve noticed, frugal with fuel.

Next up is the GL450 (MSRP $60,950) with a 335-hp gasoline V8 that scoots this impressive machine from zero-to-60 mph in under seven seconds. Not that you’re racing anyone, but you’ll certainly appreciate the confident acceleration and passing power when you’re heading out for the weekend with the family and all their stuff aboard.

At the top of the line, the GL550 with the 382-hp 5.5-liter V8 (MSRP $82,850) is also the line’s luxury leader. Every one of these machines is certified as an Ultra Low Emission Vehicle (ULEV), even in the most stringent states.

All GL models come with the ultra-smooth Mercedes-Benz seven-speed automatic transmission, and all have standard 4MATIC all-wheel drive to send the power where it’s most needed in slippery weather.

The GL is prepared for the way you use a full-capability SUV, too. Ever see somebody towing a trailer, and the trailer starts to swing a bit? In the GL, Trailer Stability Assist senses that movement and brings it under control. When you’re starting off on a steep slope, Hill Start Assist automatically holds the brakes for a moment after you release the brake pedal to help prevent rollback. A special off-road driving control program is available at the push of a button, and

Downhill Speed Regulation gives you surefooted control over rugged terrain.

Inside, nine standard airbags give you peace of mind, and the NECK-PRO active front head restraints help to reduce whiplash injuries in a rear impact. If the standard PRE-SAFE® system detects that a frontal collision or rollover is imminent, it can tighten the front seatbelts and even close the windows and sunroof.

Luxury, of course, is in abundant supply in the GL including a standard power glass front sunroof and a fixed-glass rear sunroof.

No matter which GL you prefer, you’re starting with a full-size, full-capability luxury SUV that will undoubtedly raise your expectations for such vehicles. We’re confident that only the GL will meet them.