Europeans pay twice what Americans do for fuel, so it’s not surprising that European automakers have spent decades perfecting the art of the diesel engine. Diesels typically generate greater torque and greater fuel economy than similar-sized gasoline engines, but historically commanded a greater price premium and generated greater amounts of pollution. Mercedes-Benz, and other manufacturers committed to diesel because of home-market considerations, has discovered how to make a cost-effective diesel engine that burns clean enough to meet emissions regulations in all 50 U.S. states – including rigorously strict California. Mercedes calls its latest technology BlueTec, and offers it in the company’s largest SUV, the 2009 GL-Class. We borrowed a 2009 GL320 BlueTec to see what kind of fuel economy it would return, and got 21.1 mpg on average, with an emphasis on highway driving.

Here is a summary of the changes to the 2009 Mercedes-Benz GL-Class:
• New 50-state GL320 BlueTec diesel model replaces GL320 CDI
• Pre-Safe preventive occupant protection now standard
• Keyless Go added to GL550 standard equipment
• New standard COMAND system with 6.5-inch display
• Available rear entertainment includes twin 8-inch screens
• Zagat restaurant information included with optional navigation
• Class IV (7500-pound) trailer hitch available

The 2009 Mercedes-Benz GL-Class is available in three variants: the GL320 BlueTec, the GL450, and the GL550. To the point of making diesel engines more affordable, the least expensive GL is the BlueTec model, made even more appealing by a $1,800 Alternative Motor Vehicle Tax Credit from the federal government. By comparison, the GL450’s window sticker is about $1,000 higher than the BlueTec.

Standard equipment on the GL320 BlueTec and GL450 includes full-time 4WD, an Airmatic adaptive variable suspension, 19-inch alloy wheels (20-inch wheels on the BlueTec), brown Bird’s Eye Maple wood trim with genuine aluminum accents, an 80-watt audio system with a CD changer, automatic climate control, Tele-Aid telematics, a power sunroof, a first-aid kit, and MB Tex upholstery, which is Mercedes-speak for vinyl.

In addition to a more powerful V-8 engine and a more aggressive front end design, the 2009 Mercedes-Benz GL550 adds an adaptive damping suspension feature, 21-inch AMG-design alloy wheels, power rear liftgate, a 610-watt Harmon/Kardon surround sound system with Sirius satellite radio, an auto-dimming rearview mirror, adaptive bi-Xenon headlights with heated washers, burl walnut interior trim, leather upholstery, multi-contour front seats, heated second-row seats, memory for the front seats and side mirrors, COMAND navigation with a 40-gigabyte hard drive, Parktronic front and rear parking sensors, and a cargo net.

Mercedes-Benz offers numerous options on the GL320 BlueTec and GL450. The Premium 1 Package includes a reversing camera, Parktronic parking sensors, memory for the front seats and power folding mirrors, auto-dimming interior and exterior mirrors, Keyless Go keyless locking and ignition systems, an integrated iPod interface, a power-adjustable steering column, COMAND navigation with a 40GB hard drive, Harmon/Kardon premium audio with Sirius satellite and HD radio, a power liftgate, and a 115-volt power outlet. The Premium 2 Package adds triple-zone climate control, bi-Xenon adaptive headlights with heated washers and curve illumination, and cornering fog lights.

Other option packages include an Appearance Package with additional chrome and metallic exterior trim, as well as running boards. The Appearance Package also includes 20-inch wheels on the GL450. A Full Leather Package includes leather seat upholstery, a wood-and-leather steering wheel, burl walnut interior trim, and premium interior lighting. Finally, the Heating Package includes a heated steering wheel and heated rear seats. Other options include an entertainment system, an adaptive damping suspension system, a Class IV trailer hitch, and metallic paint. The GL450 can also be equipped with active ventilated front seats, a feature not offered on the GL320 BlueTec.

The 2009 Mercedes-Benz GL550 comes with most of these features as standard equipment. The only extras that are available are a Class IV trailer hitch, a rear seat entertainment system, a heated steering wheel, active ventilated front seats, premium Nappa leather upholstery, and Light Birch wood trim. Everything else is included in its sticker price.

There are three different engines offered on the various 2009 Mercedes-Benz GL-Class models. The 2009 Mercedes-Benz GL320 BlueTec is equipped with a 3.0-liter turbodiesel V-6 engine that makes 210 horsepower at 3,800 rpm and 398 lb.-ft. of torque between 1,600 and 2,800 rpm. A seven-speed automatic delivers power to all four wheels, and this model is rated by the EPA to return 17 mpg city/23 mpg highway, burning ultra-low sulfur diesel fuel or B5 biodiesel. Our review vehicle returned an average of 21.1 mpg, with an emphasis on highway driving. Notably, during our test drive diesel fuel was selling for about 50 cents less per gallon than premium unleaded.

The most popular model, the GL450, is equipped with a 4.5-liter V-8 engine making 335 horsepower at 6,000 rpm and 339 lb.-ft. of torque between 2,700 and 5,000 rpm. It, too, is equipped with a seven-speed automatic driving all four wheels. The EPA says the GL450 gets 13 mpg in the city and 18 mpg on the highway, burning premium unleaded fuel.

In exchange for a nearly imperceptible loss of fuel economy, the Mercedes-Benz GL550 makes plenty of extra power thanks to a 5.5-liter V-8 engine making 382 horsepower at 6,000 rpm and 391 lb.-ft. of torque between 2,800 and 4,800 rpm. It’s connected to a seven-speed automatic driving all four wheels, and is rated by the EPA to get 13 mpg in the city and 17 mpg on the highway burning premium unleaded.

Standard safety equipment on every 2009 Mercedes-Benz GL-Class includes dual front airbags, a knee airbag for the driver, side-impact airbags for the front and rear seating positions, and side-curtain airbags for each outboard seating position. Additionally, the GL-Class comes standard with four-wheel-disc ABS with brake assist; a stability control system with trailer stability assist feature; and traction control. Standard Hill Start Assist holds the GL-Class in position on hills as the driver moves his or her foot from the brake to the accelerator pedal.

The GL-Class is also offered with additional standard or optional safety features, including headlights and fog lights that can help to illuminate around corners, Parktronic sensors in the bumpers that help the driver determine maneuvering space, and automatic rain-sensing wipers. There’s also a Tele Aid security and communications system, which includes an SOS button that can summon help in the event of an emergency, and provide GPS coordinates when the SUV is optioned with the COMAND navigation system. Finally, the GL-Class is equipped with standard PRE-SAFE technology, which automatically tightens the front seatbelts and positions the front seats for optimum protection when sensors indicate a crash is likely. The system can also automatically close the windows and sunroof if the sensors anticipate a rollover incident.

J.D. Power and Associates says the 2009 Mercedes-Benz GL-Class competes against other large premium multi-activity vehicles such as the Cadillac Escalade, Infiniti QX56, Land Rover Range Rover, Lexus LX 570, and Lincoln Navigator.