View Full Version : 2008 Mercedes-Benz GL320 diesel

Valentine One Radar Detector

03-11-2008, 09:27 AM
With gas prices galloping toward $4 per gallon - maybe more - even the affluent are beginning to feel the bite. Which is why a diesel-powered large SUV like the Benz GL320 CDI has a competitive edge over other high-end large SUVs that only offer gas engines - and gas mileage in the mid-low teens.

Eighteen city and 24 highway (the EPA rating for the GL320) may not be spectacular relative to a Civic - but compared to other seven-passenger premium 4WD SUVs (including the gas V-8 versions of the GL, whose highway mileage is in the 17-18 mpg range) it is a whole lot more bearable.


The GL320 is powered by a turbo-diesel 3.0 liter V-6 with common rail direct injection (CDI). It produces 215 horsepower and is teamed up with a 7-speed automatic and permanent 4WD with optionally available locking center and rear differentials, as well as skid plates and off-road aids such as Hill Start Assist, Downhill Speed Regulator, height-adjustable Airmatic suspension and an off-road driving program that adjust engine/transmission operating parameters to help you negotiate heavy mud, steep inclines, uneven trails and so on.

The little diesel's power rating may not sound all that impressive relative to the two optional gas-burning V-8s in the GL450 (4.7 liters, 335 hp) and range-topping GL550 (382 hp). However, consider the torque rating of the diesel V-6 (398 lbs.-ft.) compared to the V-8s (339 lbs.-ft. for the 4.7 liter engine; 391 lbs.-ft. for the 5.5 liter engine). The V-6 produces more torque than both V-8s and it is available at just 1,600 RPM. The gas V-8s don't produce their peak torque until you spin them to considerably higher engine speeds (2,700 RPM for both the 4.7 liter and 5.5 liter V-8s).

That means you have to work them harder - and thus, burn more fuel - to extract maximum performance. Don't be misled by the horsepower numbers; it is torque, or twisting energy, that translates into the feel of power/acceleration when you push down on the gas pedal - especially in a heavy vehicle such as the GL.

Though the gas-burning GLs are quicker, the GL320 isn't slow. It needs about 7.3 seconds to reach 60 mph. That is is only about half a second off the pace of the GL450 (appx. 6.7-6.8 seconds) and not all that far behind the blazing quick GL550 (about 6 seconds flat) but with much better gas mileage and highway range (600-700 miles on a full tank) than either of them.

Top speed is electronically limited to 130 mph; max tow load is 7,500 lbs.


Compared with other seven passenger full-frame 4WD SUVs, the GL can bust a move; it's almost agile - seriously. Drive it and see for yourself. Mercedes did a brilliant job of making the GL feel massive and solid yet not top-heavy and tipsy-feeling like other large SUVs, including Mercedes' own Gelandewagen or G-Class (in which the stability control system comes on often and frantically, even at pretty low speeds) as well as other lumbering behemoths of the road that take to corners about as well as Oprah takes to diets.

The only time I got a reality check about the size of the GL was in the parking lot at Lowes; it sometimes take a little backing up and lining up to make it fit without being too close to whatever's in the next spot. Part of this, of course, is due to today's downsized parking spots - which are sized to fit smaller passenger cars, not large SUVs. Still, there's not a lot of margin to spare. But this is no less true of any other three-row, seven passenger full-size SUV. It's just the price of doing business, so to speak. Benz does provide the usual/expected (at this price point) back-up camera and proximity sensors that beep if you're about to bump into something.

Ride quality is no less than you have every right to expect from Mercedes-Benz - and a vehicle with a base price of $53,400. I put it in the same league as the base model (not turbo) Porsche Cayenne; some give - but not too much. Firm - but not too firm. Not much body roll, even when leaned on pretty hard. Really great seats with lots of adjustment (and multi-stage heaters) help here. I spent some time in the second row to see what it was like and never felt sea sick - which sometimes happens to second (and third) row riders in vehicles this large as they sway and roll and heave around like deck hands on the Exxon Valdez.


One of the things I liked about the GL is that while it is no doubt a physically a large vehicle, it is not so overpoweringly huge in profile that it makes you feel you're piloting a Winnebago. Step-in height, for instance, is more car like than SUV-like. (The adjustable suspension has three inches of travel.) The overall shape looks more wagon/car-like than UPS truck-like. Yet it it is still a real-deal SUV with a real-deal heavy-duty chassis/suspension and real four-wheel-drive that offers no-bull equipment such as a two-speed transfer case and available locking differentials - not a car-based "crossover" with a light-duty all-wheel-drive system based on a front-drive layout.

Not that you would, but the fact is you could take the GL off-road and not make a fool out of yourself - or kill the thing in the process.

The third row, though, is what defines the GL. It is perfect for kids and teenagers - and still serviceable in a pinch for most non-obese adults. Access/usability is much enhanced by the electric/power fold-down feature for each seatback. The second row fold-away function is manually done (you pull on a level and tuck/fold them down) but the action is not heavy and neither are the seats themselves. Once the second and third row are folded flat, you have a large (83 cubic foot) cargo area big enough for a six footer to lay down on and take a snooze. It's also rated to handle weight up to 1,620 lbs and the diesel GL can tow as much as the gas V-8 GLs (7,500 lbs.)

All interior surfaces are elegantly finished; the optionally available leather is expensive in look and feel; stitched together in what look like hand-fitted sections. Even the cargo area (an out of sight part of the vehicle where some other automakers cheap out) is done up with the same high-end materials and detail-obsessive craftsmanship. My tester had the optional Burl Walnut trim, including steering wheel. Beautiful stuff.

You'll feel good about having spent what you spent.


At more than $53k before you begin adding options (my tested GL 320 topped out at $67,855) you expect nothing but the finest in fit, finish and attention to detail. And the GL absolutely delivers on all three. Nothing questionable - let alone chintzy-looking - anywhere that I could find. Competitors like the Cadillac Escalade have closed the gap over the years, but the GL (like any current Benz) remains a paragon of high style and good taste. It is not as obnoxiously (my opinion) showy as the Escalade, while offering comparable functionality/room/utility - and at least as much in the way of gadgets and technology, including optionally available twin rear seat flat screen DVD monitors, active headlights, rearview back-up camera and one-touch power liftgate.

Standard safety equipment includes pretty much everything - excellent brakes with ABS and Brake Assist, traction and stability control, rollover sensor, active head restraints, side impact air bags for first and second row - and head/curtain air bags for all three rows. The GL's 5,200 lb. curb weight and heavy-gauge materials add the inherently superior crashworthiness of size and mass.

Watch out, Smart cars.


This is a nice rig. A big rig, no doubt - but for some people, that's a necessity. But that doesn't have to mean 15 mpg is necessary - as the diesel GL clearly demonstrates.

And there's no downside, either. The diesel is exceptionally smooth and powerful; in fact, at lower speeds, it pulls harder with less pedal effort than the V-8s do. And it absolutely does not rattle like an old coffee can full of loose nuts and bolts. You'll notice a different (lower) tone when you floor it, but it's not unpleasant or unduly loud. Gas V-8s make noise, too - don't forget. The chief noticeable difference is the diesel's much lower powerband. To extract peak output/performance from the gas V-8s, you have to rev them well past 5,000 RPM. But the diesel makes its peak horsepower at just 3,800 RPM and max torque just off idle speed (1,600 RPM). Peak torque hangs with you through 2,800 RPM, too - which means the full motive force of the diesel V-6 is available sooner and lower. The result is the GL320 rarely feels stressed; just slightly depress the throttle and it moves - right now.

The same pleasant understressed feeling continues at higher speeds. The seven-speed automatic/rear axle ratio (3.45:1 vs. 3.70:1 for the gas V-8s) is geared so that very high highway speeds are possible without spinning the diesel past 3,000 rpm (which will give you 100-plus mph with the cruise control on). At more reasonable - and lawful - 70-ish speeds, the GL320 trucks along with the engine burbling around 2,300 RPM.

One oddball touch that is both retro and modern at the same time is the column-style shifter. But it is also fully electronic - so you tap it for Reverse and Drive instead of pulling and tugging on it as you might the stalk of a '77 Chevy Caprice Classic. Park is engaged by touching a button on the end of the stalk. The whole thing saves a lot of space that would otherwise be eaten up by a console-mounted gear selector - but I am a bit of a technophobe and wonder about the long-term wisdom of this very high-tech (and "drive by wire") system. (A traditional manual linkage is hard to break and fairly easy to repair if you do. And if you can't, you can usually still gimp the vehicle home. But when the GL's drive-by-wire, electronic gear selector croaks out, it's probable there'll be a tow truck - and a very big bill - in your immediate future.)

Bottom line - the GL's one of the nicest (and no compromises) seven-passenger SUVs of its type you could buy. And the availability of a powerful (but still reasonably economical) diesel engine gives the GL edge a real edge over competitors that sell gas-only (and gas-thirsty) engines in their large SUVs.

The one glitch (for the next few months, anyhow) is that the diesel GL is not sold in all 50 states (including California) because of emissions-related reasons. However, in 2009, an updated Bluetec version of the diesel GL will become available. It will offer all the advantages and appeal of the current GL320 CDI - and be available nationwide.


Disco Man
03-12-2008, 04:23 AM
Great article, I just posted it on the main site with pictures:



03-12-2008, 05:09 AM
Does the 2008 MB diesel have the piss jar in the engine compartment, or is that part of the 50-state system for 2009?

03-12-2008, 07:53 AM
Does the 2008 MB diesel have the piss jar in the engine compartment, or is that part of the 50-state system for 2009?

50 state (and next year/2009). It'll be called Bluetec....