1.AbstractThis paper reports the results obtained in the EPEFE programme on the relationships between diesel fuel properties and light duty vehicle technology, which were used as input for further studies (i.e. air quality modelling) within the framework of the European Auto-Oil programme.The effects of density, polyaromatics, cetane number and back-end distillation (T95) were investigated in' 17 light duty vehicles and 2 light duty trucks which were selected to reflect the range of technologies and vehicle configurations anticipated to meet predicted emissions requirements beyond 1996. All were fitted with oxidation catalysts.The measured pollutants included total hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx) and particulates (PM) as well as hydrocarbon speciation and compositional analysis of particulates, tested to the European driving cycle for the year 2000.For the vehicle fleet as a whole, the largest percentage fuel effects were observed for HC, CO and PM. Linear regression equations were derived expressing fleet emissions in terms of the four targeted fuel properties. The interaction of fuel density with engine management systems (EMS) was also investigated, specifically the extent to which the observed density effects on emissions were affected by tuning the EMS.Significant differences in both emission levels and response to fuel property changes were observed between vehicles, and explanations for these observations are proposed in terms of specific vehicle technologies employed.Overall, the results of the programme confirmed that it is necessary to consider fuel properties and engine technology together in order to arrive at possible further optimisation of emissions performance.