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Automotive diesel fuel has traditionally been produced by atmospheric distillation of crude oil to provide a product meeting the requirements of diesel engines and their operators. More recently there has been a need worldwide to increase supply of diesel fuel relative to other petroleum fuels and this has led to the increased use of catalytically cracked blendstock, and a review of properties limiting product yield. This paper describes some of these key properties including the boiling range, low temperature performance, cetane number and storage stability. The performance of extended boiling range fuels in automotive equipment and their effect on emissions is discussed as are changes in ignition quality characterised by cetane number. Increased product yield by means of selected low temperature flow improvers is discussed with reference to field trials in Australia.

Within EPEFE the relationship between exhaust emissions of five 1996 heavy duty engines including advanced technologies and an eleven diesel fuel matrix has been investigated. The fuel matrix was designed to study the effects of decorrelated fuel properties (density, polyaromatics, cetane number, back-end volatility (T95)). The main programme consisted of engine testing on the 88/77 EEC test cycle at standard engine settings. The findings were quantified using regression equations and showed, that fuel effects varied in both magnitude and direction between the four emission components. Individual engines had different emission levels and responded differently to fuel properties, due to engine technology. Additional tests were conducted with selected fuels at adjusted engine settings and timing. The observed density effect on emissions can be compensated for and fully explained by physical interactions with the injection system.