Rudolf Diesel designed his namesake engine in 1897 to operate on peanut oil, a clean, renewable power source. But makers of petroleum-derived diesel fuel cornered the market early—Mercedes first put a diesel engine in the 1936 240D—and consequently diesel engines became synonymous with noisy and malodorous machinery. However, the $59,000 Mercedes-Benz GL320 BlueTEC (www.mbusa.com) could be an image-changer for diesel power. The GL320 BlueTEC is powered by a turbocharged clean-diesel engine paired to a refined 7-speed automatic transmission. The 3-liter V-6 churns out a stump-pulling 398 ft lbs of torque and gets about 23 mpg, which gives the vehicle a range of 600 miles.