Ultra-low sulfur diesel was proposed by EPA as a new standard for the sulfur content in on-road diesel fuel sold in the United States since October 15, 2006, except for rural Alaska. California required it since September 1, 2006, and rural Alaska will transition all diesel to ULSD in 2010. This new regulation applies to all diesel fuel, diesel fuel additives and distillate fuels blended with diesel for on-road use, such as kerosene, however, it does not yet apply to train locomotives, marine, or off road uses. By December 1, 2010, all highway diesel will be ULSD. Non-road diesel transitioned to 500 ppm sulfur in 2007, and to ULSD in 2010. Locomotive and marine diesel also transitioned to 500 ppm sulfur in 2007, and to ULSD in 2012. There are exemptions for small refiners of nonroad, locomotive and marine diesel that allow for 500 ppm diesel to remain in the system until 2014. After December 1, 2014 all highway, nonroad, locomotive and marine diesel produced and imported will be ULSD.
The EPA mandated the use of ULSD fuel in model year 2007 and newer highway diesel fuel engines equipped with advanced emission control systems that require the new fuel. These advanced emission control technologies will be required for marine diesel engines in 2014 and for locomotives in 2015.
The allowable sulfur content for ULSD (15 ppm) is much lower than the previous U.S. on-highway standard for low sulfur diesel (LSD, 500 ppm), which not only reduces emissions of sulfur compounds (blamed for acid rain), but also allows advanced emission control systems to be fitted that would otherwise be poisoned by these compounds. These systems can greatly reduce emissions of oxides of nitrogen and particulate matter.
Because this grade of fuel is comparable to European grades and engines will no longer have to be redesigned to cope with higher sulfur content and may use advanced emissions control systems which can be damaged by sulfur, the standard may increase the availability of diesel-fueled passenger cars in the U.S. European diesels are much more popular with buyers than those available in the U.S.
Additionally, the EPA is assisting manufacturers with the transition to tougher emissions regulations by loosening them for model year 2007 to 2009 light-duty diesel engines. As a result, Honda, Nissan, Subaru, Toyota, and others are expecting to begin producing diesel vehicles for the U.S. market to join those from Mercedes-Benz and Volkswagen.
According to EPA estimates, with the implementation of the new fuel standards for diesel, nitrogen oxide emissions will be reduced by 2.6 million tons each year and soot or particulate matter will be reduced by 110,000 tons a year.
On June 1st, 2006, U.S. refiners were required to produce 80% of their annual output as ULSD (15 ppm), and petroleum marketers and retailers were required to label diesel fuel, diesel fuel additives and kerosone pumps with EPA-authorized language disclosing fuel type and sulfur content. Other requirements effective June 1st, 2006, including EPA-authorized language on Product Transfer Documents and sulfur-content testing standards, are designed to prevent misfueling, contamination by higher-sulfur fuels and liability issues. The EPA deadline for industry compliance to a 15 ppm sulfur content was originally set for July 15, 2006 for distribution terminals, and by September 1, 2006 for retail. But on November 8, 2005, the deadline was extended by 45 days to September 1, 2006 for terminals and October 15, 2006 for retail. In California, the extension was not granted and followed the original schedule. As of December, 2006, the ULSD standard has been in effect according to the amended schedule, and compliance at retail locations was reported to be in place.
Sulfur is not a lubricant, however the process used to reduce the Sulfur also reduces the fuel's lubricating properties. Lubricity is a measure of the fuel's ability to lubricate and protect the various parts of the engine's fuel injection system from wear. The processing required to reduce sulfur to 15 ppm also removes naturally-occurring lubricity agents in diesel fuel. To manage this change ASTM International (formerly the American Society for Testing and Materials) adopted the lubricity specification defined in ASTM D975 for all diesel fuels and this standard went into effect January 1, 2005.
The refining process that removes the sulfur also reduces the aromatic content and density of the fuel, resulting in a minor decrease in the energy content, by about 1%. This decrease in energy content may result in reduced peak power and fuel economy. The reduction is only slight and will likely go unnoticed.
ULSD will run in any engine designed for the ASTM D-975 diesel fuels.