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Shell companies* and Mercedes-Benz have investigated the effect of diesel fuel properties on exhaust emissions in an advanced European IDI passenger car and a modern commercial vehicle DI engine. The experimental programme identified the key fuel properties that influence diesel engine emissions with specific emphasis on NOX and particulates emissions. The fuel properties investigated were density, sulphur, distillation range, cetane number, mono aromatics and polyaromatics content. With regards to the polyaromatics content, the fuels were not designed to differentiate between the effect of di- and tri+ -aromatics. It is concluded that the fuel properties which account for the observed fuel effects on particulates emissions are sulphur, density and polyaromatics content. Monoaromatics content, cetane number and the distillation, as described by T10E, T50E and T90E, were found to have no effect on particulates emissions.

Europe is currently on the threshold of introduction of unleaded gasoline. However, this will not proceed uniformly, as some countries such as Germany. Austria. Switzerland and now Scandinavia are moving much more quickly than others. In those countries where unleaded fuel is available, registrations of catalyst cars and the build-up of the gasoline retail network and sales volumes are described. Possible future developments in these areas are discussed. The potentials and limitations on the manufacture of unleaded gasoline are discussed together with the role of oxygenates. The development of specifications in various countries is described and on the basis of market surveys actual quality is compared with the minimum requirements of these specifications. Results of road tests are presented showing the effects of both gasoline with maximum lead content and engine oil with a relatively high phosphorous content on deterioration of catalyst efficiency.