Those of you with a passing familiarity with diesels are probably thinking-mileage and reliability aside-"Aren't diesels heavy, low-horsepower lumps that are loud, smelly and best suited for plowing fields and lifting heavy loads?" Well, yeah, they can be, especially the older ones. However, tightening noise and emissions laws as well as economic factors have forced diesel manufacturers to ramp up efforts to resolve those issues. The results-achieved partly by going to lighter materials, such as aluminum in engine blocks, and partly with enhanced technologies like computer-controlled common-rail injector systems that better manipulate fuel delivery-have paid off handsomely. The latest generation of diesels, particularly those in cars and light trucks, are civilized, relatively clatter-free, and display surprisingly good performance.