The Mercedes-Benz GL-Class of full-size SUVs gets greener for 2009, thanks to the GL320, which now comes equipped with a next-generation 3.2-liter BlueTEC V6 turbodiesel engine. The fuel-efficient and emissions-friendly engine injects an ammonia-rich urea-based fluid called AdBlue into the engine's exhaust stream to change nitrogen oxides in the engine's exhaust stream into harmless nitrogen and water. Due to emissions problems, previous versions of the diesel-powered GL320 were barred from sale in a number of states, including California, New York, and Pennsylvania. But Mercedes will offer the '09 GL320 BlueTEC SUV for sale in all 50 states.

The GL320's BlueTEC engine produces an acceptable 210 hp and 398 lb-ft of torque at 1,600 rpm, resulting in good acceleration and a spirited ride around town. However, performance suffers a bit at passing speeds, according to reviewers. On the other hand, the GL320 manages about 24 mpg on the highway and 18 in the city, which are respectable numbers for a full-size SUV.

The BlueTEC engine links to a seven-speed automatic transmission, which adds to the SUV's smooth acceleration and fuel efficiency. Drivers should be aware that the AdBlue reservoir must be refilled every 10,000 miles or so, which Mercedes dealers will do during regularly scheduled oil changes. However, drivers who use the GL320 for frequent towing may have to refresh the AdBlue reservoir more frequently.

As in the previous year, the GL-Class also includes the GL450 and GL550, which change little for 2009. A 335-hp, 4.5-liter V8 drives the GL450, which features leather upholstery, hand-polished wood trim, a ride-balancing suspension, and a 7,500-pound towing capacity. The GL550 retains its 382-hp, 5.5-liter V8, which drives the big SUV from 0 to 60 in 6.4 seconds. Other features of the GL550 include multicontour front seats with 10-way power adjustment, a power tailgate, a DVD-based navigation system, and brown Birdseye Maple wood trim. All GL-Class SUVs feature 4Matic four-wheel drive and seat seven passengers.