[The Christian Science Monitor] Refineries are beginning to make low-sulfur fuel, under a new EPA rule. Cleaner engines to follow. For as long as people have cared what wafts from vehicle tailpipes, diesel motors have had the rap as the dirtiest, smelliest, noisiest engines on the road. That could soon change. In a move that may presage diesel’s Cinderella-like transformation, the Environmental Protection Agency on Thursday required U.S. refineries to begin making ultra-low-sulfur diesel (ULSD), a fuel with 97 percent less sulfur than ordinary diesel that, as a result, slashes soot emissions.