The GL-Class is sold with a variety of engines. The GL 320 CDI gets a Bluetec 3 liter diesel engine making 224 hp, the GL 420 CDI gets a 4 liter V8 diesel engine making 302 hp, the GL 450 gets a 4.6 liter gasoline V8, the GL 550 gets a 5.5 liter V8, and the high performing GL 63 AMG gets a 6.3 liter V8 engine making 475 horsepower. The transmission is a 7 speed automatic, with no manual option yet offered.
The Bluetec diesel is special because it does one thing that few diesel engines can do: outputs clean emissions. It has a system to clean emissions using urea, which makes it one of the few high performing diesel engines to be legal in all 50 states in the U.S. The urea injection system does not get introduced until 2009, but it will still be one of the cleanest diesels out there even before then.
This SUV was supposed to replace the G-Class, but public demand has kept the G-Class alive.
These cars are selling for a hefty sum, and for a good reason. They offer both luxury and high performance. You'll start seeing these hit eBay within the next year as some of the older models get unloaded off dealer lots, and as luxury fleets decide to upgrade. Be ready to pick up some good deals when they do get listed.