The visually and intellectually green state of Vermont proved a fitting location for the introduction of the newest additions to Mercedes' growing 50-state clean-diesel family. Surrounded by lush foliage (and quite a few bumper sticker-adorned
Subaru wagons), the ML, R and GL 320 BlueTEC SUVs did little to disrupt the quiet -- or fresh air -- of the quaint countryside, further demonstrating that the diesels of today are nothing like the noisy, smelly and dirty versions many remember. Replacing Mercedes' Common-rail Direct Injection (CDI) diesel engine, the 3.2-liter turbocharged and direct-injected unit under each hood delivered plenty of low-end torque, and we found that all three test vehicles averaged 21-24 miles per gallon, even with the occasional lead foot. The only complaints during our day and a half of driving were directed at an upper-end power deficiency that made highway passing more, uh, exhilarating than usual, even with the help of a seven-speed automatic transmission. If we were buying today, however, we'd take the diesel version of each one of these cars.