Ultra-low-sulfur diesel (ULSD) is diesel fuel with substantially lowered sulfur content. Since 2006, almost all of the petroleum-based diesel fuel available in Europe and North America has been of a ULSD type. The move to lower sulfur content allows for the application of advanced emissions control technologies that substantially lower the harmful emissions from diesel combustion. Testing by engine manufacturers and regulatory bodies have found the use of emissions control devices in conjunction with ULSD can reduce the exhaust output of ozone precursors and particulate matter to near-zero levels. In 1993 the European Union began mandating the reduction of diesel sulfur content and implementing modern ULSD specifications in 1999. The United States started phasing in ULSD requirements for highway vehicles in 2006, with implementation for off-highway applications, such as locomotive and marine fuel, beginning in 2007.
Lubricity Sulfur is not a lubricant in and of itself, but it can combine with the nickel content in many metal alloys to form a low-melting eutectic alloy that can increase lubricity. 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 D975 standard defines two ULSD standards, Grade No. 2-D S15 (regular ULSD) and Grade No. 1-D S15 (a higher volatility fuel with a lower gelling temperature than regular ULSD). 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 slightly reduced peak power and fuel economy. ULSD runs in any engine designed for the ASTM D975 diesel fuel, however, it is known to cause some seals to shrink, and may cause fuel pump failures in Volkswagen TDI engines used in 2006 to pre-2009 models. TDI engines from 2009 and on are designed to use ULSD exclusively; biodiesel blends are reported to prevent that failure.
Africa
Kenya Some filling stations in Kenya started offering 50 ppm diesel as of December 2010. As of 2018, Kenya has not fully implemented emission control systems.
Mauritius As of June 2012, 50 ppm diesel is now standard across all filling stations, in a bid to reduce pollution.
Morocco Morocco has started to introduce 50 ppm diesel to filling stations as of 2009. Since 2011, the 10 ppm diesel has been available in some filling stations. A generalization to all filling stations with the 10 ppm diesel is available since December 2015.
South Africa 50 ppm sulfur content was first legislated by the South African Department of Minerals and Energy in early 2006, and has been widely available since then. South Africa's Clean Fuels 2 standard, expected to have begun in 2017, reducing the allowable sulfur content to 1 ppm. As of 2013, Sasol launched 10 ppm diesel at selected filling stations.
Asia
Saudi Arabia Euro-II gasoline and diesel standards. In 27th February 2024, the Saudi Ministry of Energy announced the successful introduction of Euro 5 standard diesel fuel and gasoline across the Kingdom of Saudi Arabia.
China China has limited sulfur in diesel fuel to 150 ppm (equivalent to the Euro III standard). The limits of 10 ppm (equivalent to the Euro V standard), only apply in certain cities such as Beijing. From 2014 to 2017, China will limit sulfur in diesel fuel to 50 ppm. After 2017, the sulfur content in diesel fuel will be limited to 10ppm.
Hong Kong In July 2000, Hong Kong became the first city in Asia to introduce ULSD, with sulfur content of 50 parts per million (ppm). In addition, new petrol private cars were asked to meet Euro III standards from 2001. Since the introduction of the law, all fuel station started supplying ULSD since August 2000. Sulfur content of regular diesel fuel was lowered from 500 ppm to 350 ppm on 1 January 2001. As part of the ULSD package, Hong Kong government lowered the tax for ULSD from HK$2.89 to $2.00 per liter in June 1998. The temporary concession was extended to 31 March 2000, then to 31 December 2000. On 19 June 2000, under Report of the Subcommittee on resolution under section 4(2) of the Dutiable Commodities Ordinance (Cap. 109), ULSD fuel tax was lowered to HK$1.11 per liter between 7 July 2000 and 31 December 2000, then increased to $2 in 2001, then $2.89 per liter on 1 January 2002. This resolution was passed on 27 June 2000. Castle Peak Power Station was designed to burn heavy fuel oil for boiler startup, flame stabilization and occasionally as a secondary fuel. Since the early 2010s, all boilers were converted to burn ULSD to cut down sulfur dioxide emission. On the other hand, Black Point Power Station and Penny's Bay Power Station were designed to burn ULSD as a secondary and primary fuel respectively. So all power stations under CLP Power burn ULSD instead of higher sulfur alternatives now.
Pakistan Pakistan began importing Euro-V standard fuel in mid 2020. The import of Euro-V petrol was started on August 10, 2020, while all diesel imports of the country will conform to Euro-V standard by January 2021. The shift was carried out directly from Euro-II to Euro-V.
India Delhi first introduced 50 ppm sulfur diesel on 1 April 2010 as a step aimed at curbing vehicular pollution in the capital. This was done in 12 other cities at the same time. The sulfur content in the diesel being used was 350 ppm. There are two types of diesel available in India from year 2010. Bharat Stage IV (equivalent to Euro IV) specification having Sulfur level below 50 ppm is available all over the country and the Bharat Stage VI with ultra low sulfur was slowly introduced in New Delhi in April 2018. The Bharat Stage VI with ultra low sulfur content of less than 10 ppm will be standard across the country from April 2020.
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