Car Culture

Mercedes-Benz GL320 BlueTEC beats EPA mpg

While its cabin tech feels dated, the 2009 Mercedes-Benz GL320 BlueTEC delivers very good fuel economy for a vehicle of its size.

Mercedes-Benz GL front bumper
We may have saved a few mpg on our road trip, but we didn't do any favors for the insect life along I-5. Corinne Schulze/CNET

We were recently given the opportunity to take the 2009 Mercedes-Benz GL320 BlueTEC on a long-distance road trip from San Francisco to Los Angeles and back. While this seven seated behemoth was probably not the best vehicle to transport one journalist across the state of California, we figured this long trip down Interstate 5 would be a good opportunity to see how close the fuel-efficient diesel powerplant could get to its EPA estimated mileage.

The powerplant in question is a 3.0-L turbodiesel V-6 that outputs 210 horsepower and a beefy 398 pound-feet of torque. The engine sends its power through a seven-speed adaptive automatic transmission to Mercedes-Benz's 4MATIC permanent all-wheel drive system. Keeping the diesel's emissions clean is an AdBlue injection system that scrubs up to 80 percent of NOx from the exhaust gases. Greenies will be happy to know that the BlueTEC diesel is also approved for use with B5 biodiesel.

On the road, the 398 pound-feet of torque doesn't translate into neck-snapping acceleration. Perhaps this is because of the GL's immense weight; perhaps it's the turbo lagging; or maybe Mercedes has tuned some of the throttle response down to create more refined and fuel efficient acceleration. Whatever the cause, the GL320 feels sluggish off of the line. Really putting your foot into the accelerator and waiting for the turbodiesel to build steam eventually results in that torquey diesel thrust that we're used to, but the acceleration is uneven and slightly unpredictable.

Once the GL320's BlueTEC diesel settles into its groove, such as during highway cruising, power remains strong, allowing the GL to pass/merge with ease and coast along at freeway speeds while taking advantage of the transmission's tall seventh gear to keep the revs low.

Mercedes-Benz GL320
The GL's default suspension mode is good enough for most situations. Corinne Schulze/CNET

Our GL320 was equipped with the optional Adaptive Damping System, which adds a Sport mode and a Comfort mode to the suspension's Default setting. The three modes felt noticeably different, with Sport mode transmitting a good deal of expansion joint harshness into the seat bottom and Comfort mode feeling floaty and vague. The GL isn't an athletic vehicle in any mode and the Default mode was more than sufficient for most situations, causing us to question the utility of the $750 option.

Speeding down Interstate 5, cruise control holding the SUV at a steady 75 mph, the GL's leather appointed cabin isolated its passenger from road and wind noise. The leather-trimmed seats were quite comfortable for the seven-plus hour trip, but the high seating position had us feeling like we were sitting on top of a vehicle rather than inside of one. The vague feedback through the steering and suspension made us feel even more isolated from the driving experience, but somehow we think that's the point of driving a vehicle this large. On the bright side, the power steering was light and quite responsive to inputs.

Fortunately, the GL320's cabin tech package was able to keep us entertained where the ride did not. iPod connectivity, a six-disc DVD/CD changer, and in-dash SD card reader join AM/FM/HD radio and Sirius satellite radio on the list of available sources. Because of our lack of passengers, neither the DVD playback option nor the dual-screen, seatback-mounted rear seat entertainment system got too much of a workout on this particular trip.

All audio is routed through a Harmon/Kardon Logic7 surround sound system that sounds fantastic in the GL's quiet cabin.

GL320 interior
The cabin was well appointed, if not a bit dated. Corinne Schulze/CNET

Pointing us in the right direction was the 6.5-inch full color navigation system with traffic. The 40GB hard drive that holds the system's map data reserves a 4GB Music Register for ripping audio files. The system features quick routing and POI search and a fairly intuitive on-screen interface, but the archaic COMAND directional-pad-based control scheme and the lack of a touch screen required more attention to operate than we were comfortable with in a moving vehicle. The graphics are crisp, but pale in comparison to the beautiful visuals seen on newer Lexus navigation systems.

As we reached our destination, the GL320's trip computer was reporting an astounding 26.3 miles per gallon for the trip. Okay, so 26.3 mpg isn't exactly "astounding," but when you consider that the GL is a huge seven-passenger SUV, we're grateful for every mile per gallon gained. Consider that that the gasoline-powered variants average 18 highway mpg, at best, and that the GL320 BlueTEC's V-6 generates more torque than the GL550's 5.4-L gasoline V-8, and the fuel economy advantage is even more impressive.

The price you pay to shuttle seven human beings around without breaking the bank at the pump starts at $58,200 for a nicely equipped 2009 Mercedes-Benz GL320 BlueTEC. We'd skip the $750 Adaptive Damping system, but suggest that you spec the $6,600 P01 package, which includes almost every tech option available to the GL. Distract back seat drivers with the $1,850 rear seat entertainment system. Finally, add $875 and $720 for genuine leather/wood trim and special Capri Blue paint, respectively, for an as-tested price of $71,125 (including $875 destination).

After a good night's sleep, it was time to load back into the GL320 for the return trip home. We reset the trip computer and attempted to duplicate our better-than-EPA results. However, this time we encountered two long hours of LA rush hour traffic.

Many miles (and hours) later, we checked the trip computer on the GL320 BlueTEC as we parked it in the Car Tech garage. Even with a healthy dose of stop and go traffic, the GL still managed to average 23.5 mpg for the return trip, again besting the EPA rating by half a mpg.