For the record diesel is a fuel not a gas. Having said that i believe there may some corrections needed to understand what is assumed the US market and the fuel sold here.

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 will transition to 500 ppm sulfur in 2007, and to ULSD in 2010. Locomotive and marine diesel will also transition 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 particulates.

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.[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]

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