The adverse effects of sulphur to health and the environment have caused limits to be set for its content in diesel fuel. For example, the maximum sulphur content in the EC Directive 98/70/EC and US Environmental Protection Agency is 50 ppm (starting from year 2005) and 15 ppm (from October 2006), respectively. As a result, the production of ultra low sulphur diesel (ULSD) is increasingly. However, with the benefits come also the attendant problems. The hydro-treating process to remove sulphur, also removes some of the natural occurring lubricating properties. As diesel is used to lubricate the engine prior to its combustion, this poses a problem. Thus, the lubricity loss would have to be replaced. Indeed, lubricity has been included in the European automotive diesel fuel standard (EN590) since 1999, some of which are shown in Table 1.

Main Research: Cheng Sit Foon