As for the Harmon-Kardon Logic7 stereo, a premium upgrade, it sounds very good, but doesn't really have enough speakers to fill the cavernous interior. On our car, we had a single-disc slot behind the LCD and a six-disc changer in the glovebox. Both played MP3 CDs, but we were disappointed to see that only file names were displayed on the LCD, rather than full ID3 track information. We also had Sirius satellite radio.
As for hands-free calling, the GL320 is still stuck with a dedicated cell phone cradle system, as we've seen on past Mercedes-Benzes. More recently updated models are going to Bluetooth wireless connections. Our GL320 came with a rear-seat DVD option. The screens, set behind the head rests on the front seats, are well-placed and look good. But the DVD player itself is set under the right rear passenger seat, making it impossible to see. You have to insert and eject DVDs, or plug other audio/visual gear into its RCA jacks, by feel.
Parking is helped by one of the clearest rearview cameras we've seen, although it lacks any overlay to show how close you are to an obstruction or where your wheel turn will take you. And being a big luxury SUV, it has niceties such as a powered lift gate and buttons to make the third-row seats fold flat or open up.
Under the hood
We had previously reviewed the 2007 Mercedes-Benz GL450, which uses a 4.6-liter V-8 instead of our GL320's turbocharged 3-liter diesel V-6. The GL450 felt fast, jumping quickly off the line. The diesel-powered GL320 feels a little more sluggish, as if all of its components need to make a collective decision to accelerate when you hit the throttle. But after this initial hesitation, it builds speed nicely. Most people wouldn't even realize it has a diesel engine. This engine makes 215 horsepower and 398 ft-lbs of torque, that peculiar diesel mix that works very well in a vehicle that weighs in at 5,313 pounds.
We covered our mileage on a trip (above) that favored highway driving. Overall we saw an average of 21.2 mpg, landing right in between the EPA's estimated 18 mpg city and 24 mpg highway. Emissions ratings weren't published at the time of this review.
The GL320 uses Mercedes-Benz's seven-speed automatic transmission, with a manual selection mode activated by buttons on back of the steering wheel spokes. In this application, the transmission lets the engine get up to around 4,500rpm before shifting under heavy acceleration. During our driving, we never felt this transmission make aggressive downshifts, but the GL320 isn't the kind of vehicle that could make use of it. In corners, we felt body roll that suggested we shouldn't push it very fast.
No, the GL320 is a big SUV, with Mercedes-Benz's 4Matic all-wheel-drive system and a couple of tricks to help it out in off-road situations. Although ours didn't come with the off-road package, its air suspension lets you raise it up to its highest clearance, at 10.9 inches. Another button lets you put it in general off-road mode, designed to maximize traction. It also has hill descent control, and it even lets you set the speed for this function. And the safety equipment is complete, as we would expect from Mercedes-Benz, with traction and stability control.
The 2008 Mercedes-Benz GL320 CDI comes in at a base price of $53,000. Options on our test car included the Premium II Package for a whopping $8,600, the $2,100 full leather package, and another $2,670 for the rear-seat DVD system. Along with $700 for the paint and the $775 destination charge, the total came out to $67,855. The Premium II Package includes most of the cabin gadgets, such as Sirius satellite radio and navigation.
The GL320 is a pricey package, but if you're looking for a full-size luxury SUV, its diesel engine efficiency represents an incredibly compelling argument. Compared to its gasoline counterpart, the GL450, or Land Rover's Range Rover, the GL320 can transport the same number of people and as much cargo. Both gasoline SUVs have more horsepower, but the high torque of the GL320 gives it an edge in this high weight category. If you insist on gasoline, you can get the same level of luxury, mileage, and a little bling with next year's Cadillac Escalade Hybrid. Our only reservations about the GL320 are the cabin electronics, which should improve substantially with the next model update.