Ultra-low sulfur diesel

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Ultra-low sulfur diesel (ULSD) describes a new EPA standard for the sulfur content in on-road diesel fuel sold in the United States, beginning October 15th, 2006, except for California which must be selling it by September 1st, 2006. 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. The EPA is also mandating the use of ULSD fuel in model year 2007 and newer diesel fuel engines designed for on-highway use. The EPA rule goes into effect for non-road, locomotive, and marine (NRLM) diesel fuel on June 1st, 2007.

The allowable sulfur content for ULSD (15 ppm) is much lower than the previous U.S. 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 particulates.

Because this grade of fuel is comparable to European grades, this standard may increase the availability of diesel-fueled passenger cars in the U.S., since engines will no longer have to be redesigned to cope with higher sulfur content. European diesels are both more advanced technologically and 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.^[1] 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.^[2]

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, 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 will be following the original schedule.

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 the American Society for Testing and Materials (ASTM) adopted the lubricity specification defined in ASTM D975 for all diesel fuels and this standard went into effect January 1, 2005. ^[3]

There may also be a minor decrease in the energy content, by about 1%. This decrease in energy content may result in reduced fuel economy. To achieve the sulfur requirements for the new fuel standards, diesel manufacturers include an additive to keep the fuel flowing smoothly, and to prevent engine damage. A relatively cheap lubricious additive is biodiesel.

ULSD will run in any engine designed for the ASTM D-975 diesel fuels.