First, heavy-duty trucks had stricter standards for diesel sulfur content. Now, locomotives, most marine vessels and land-based non-road engines must use lower sulfur fuel.
The U.S. Department of Environmental Protection established a regulation in 2004 that refineries must reduce sulfur from current levels of about 3,000 parts per million in non-road diesel fuel to a maximum of 500 ppm, with few exceptions, beginning June 1, 2007.
Also this month, department rules became effective requiring 80 percent of highway diesel to have an ultra-low-sulfur level of 15 or fewer ppm.
In 2010, sulfur levels in most non-road diesel fuel will be reduced to the same ultra-low requirement now in effect for highway diesel, making it possible for engine manufacturers to use advanced emissions control systems that significantly reduce harmful pollutants. However, for locomotive and marine fuel, this step will occur in 2012.