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Total aromatics have no influence on particulate emissions. This is an unexpected finding from a comprehensive programme to determine the influence of diesel fuel properties on heavy-duty particulate emissions. 30 fuels and five engines representing a variety of manufacture/technology were tested. To reveal causative influences, key fuel properties were intentionally uncorrelated and had a wide range of values. Engine sensitivities to fuel quality were found to differ considerably. Properties that most influenced emissions were sulphur content, density and cetane number. Some engines were totally insensitive to polyaromatics but in others, small influences are possible. The emissions benefits of specific fuel property changes are quantified.

Following a small scouting programme to examine the scale of emissions benefits achievable by different degrees of gasoline base fuel redesign (SAE 930372), a larger programme has been initiated to investigate more systematically the influence of individual fuel parameters on tailpipe emissions. This coordinated study has been spread across five participating Shell Group laboratories, using a set of common fuels specifically designed and centrally blended for this purpose. Additionally, subsets of these fuels have been used for detailed systematic examination of selected topics within the overall programme scope. This paper summarises the plan for the integrated study. It describes the composition and properties of the fuels and their blending. The results covered here are those of chassis dynamometer-based regulated emissions studies conducted on a composite fleet designed to represent a range of vehicle technologies, using a variety of regulatory driving cycles.