The GL350 Bluetec rides and handles as well as anything in the full-size luxury SUV segment, and its interior is appropriately luxurious. Despite its problems, it's also a strong seller in its class. Perhaps its most formidable challenge, however, is the stricter fuel economy standards that loom on the horizon.

Whether through eliminating weight, downsizing drivetrains or adding advanced technology, automakers will need to increase the efficiency of big SUVs. Even the Bluetec diesel version of the GL may need to become more efficient. All these steps are likely to raise vehicle prices, so if you're interested in a big luxury SUV as it is today, you may want to act soon.