2008 Mercedes-Benz GL320 CDI

Mention diesel and images of black smoke, grease, noise, and air pollution still come to mind for most Americans. Well, Mercedes-Benz is a brand hard at work to eliminate those stigmas, all while boosting fuel economy, with its BlueTec diesels. And nowhere does this approach make more sense than in large sport utility vehicles. But can even BlueTec make this full-size 7-passenger GL-Class SUV socially acceptable?

Hot button phrases like ‘full-size SUV’ and ‘premium luxury’ are generally considered fighting words to those cut from a greener cloth.  But advanced clean diesel technology is making the largest and most gas-guzzling utilities more fuel efficient and earth-friendly: case in point, the 2008 Mercedes-Benz GL320 CDI.

Government Fuel Economy ratings for this 7-passenger V6 turbocharged diesel SUV are 18 city/24 highway. That betters the gas-V8 GL450 by about 30%. We achieved an impressive 23.8 miles-per-gallon in real world driving. Its Energy Impact Score of 19.7 barrels of oil consumed per year is still high, but also much improved.

But, while the 2008 GL320 CDI produces far less smog-forming nitrogen oxides than older light duty diesels, it’s still not clean enough to meet the strict standards of California and the Northeast.  So, late this year, Mercedes-Benz will launch BlueTec versions of the GL, ML, and R-Class SUVs. Blue Tec’s urea-injection will take clean-diesel technology to the next level, and will be 50-state legal.

With a 600 mile+ range, the GL CDI’s powertrain consist of Mercedes’ third generation common-rail direct injection turbocharged 3.0-liter diesel V6. It yields 215 horsepower and a truck-worthy 398 pound-feet of torque.  That’s more low-end power than the 450’s gas V8, so a 7,500 pound towing capacity remains.

The 320 shares the 450’s 7-speed automatic transmission which allows for manual gear change by steering wheel controls.

Also the same is the seamless 4MATIC single-speed all-wheel-drive system with four-wheel traction control. Hill-Start Assist and Downhill Speed Regulation are also included for able all-terrain prowess. Track prowess delivered 0 to 60 runs of 8.1 seconds, with the quarter-mile at 16.3 seconds at 85 miles-per-hour. Both results are slower than the 450 we tested last year, but still above average for a full-size SUV. The 320’s diesel delivers a big torque hit right off the line. From there, power builds smooth and steady, with quick, seamless shifts.

The GL’s unit body frame is supported by an Airmatic height adjustable suspension with double-wishbones up front, and a four-link geometry in the rear.  Electronic Stability Program is naturally included, all making our two-and-a-half-ton tester surprisingly nimble for its class.  There is no clunky, top-heavy feeling. And, while more steering feedback would be great, the GL stays well-planted and charged through the cones with confidence.

Brakes are four-wheel discs with standard ABS and Brake Assist Plus.  We gauged fade-free stops of 129 feet from 60 to 0 as stable and solid.

Outside, the GL wears an aggressive and modern look, similar to the smaller M-Class. Up front is a big bold grille and power-dome hood, flanked by available bi-zenon steerable headlights.

The tall, slab-sided profile is underlined by a long 121.1 inch wheelbase. That’s 5 inches longer than a Chevy Tahoe. Though 19-inch alloy wheels are optional, our tester rode atop standard 18 inchers.

Beyond the GL’s doors, that long wheelbase provides an expansive 3-row cabin that is laden with luxury, but also has an air of sport that is clearly influenced by AMG.

The upscale IP is headlined by large, clear gauges, and is trimmed with Birds-eye Maple.  Our GL’s plush seats were wrapped in fine grain leather with heat, and overhead, the sky can open up through optional dual sunroofs.

Indeed the sky is the limit as to comfort and convenience with available tri-zone automatic climate control, Harmon/Kardon stereo, and DVD navigation with voice activation and backup camera. As before most features are controlled by Mercedes’s complicated COMAND interface system.

The roomy second row offers an optional rear seat DVD system with two headrest screens.

The power-folding two-person third-row bench provides enough room for larger children.  With all seats folded down, there is a very smart 83.3 cubic feet of cargo space.

Mercedes is also smart about its diesel pricing. The GL320 CDI starts at $54,225. That’s $2,500 less than the gas GL450. But, be warned, options can push it up to the lofty $67,855 of our test rig.

While the 2008 Mercedes-Benz GL320 CDI is not the ultimate big green machine, advanced diesel technology is making it and other full-size SUV’s more environmentally acceptable. That’s great news for the big families, and trailer towers that need these big rigs. Plus, with 50-state BlueTec on the way, that acceptance is bound to grow.