Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have been exploring development avenues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential.A research program, carried out by IFP (Institut Français du Pétrole), and supported by FSH (Fonds de Soutien aux Hydrocarbures), IFP, PSA-Peugeot-Citroën, Renault and Renault VI (Véhicules Industriels), has been built to study this point. It is a four years programme with different steps which will focus on new engine technologies: some of them are going to be marketed very soon (gasoline direct injection car engine, and diesel common rail injection car and truck engines) to anticipate the Euro 3 (2000) and the Euro 4 (2005) emissions specifications.The original work reported here is part of this research. Its aim was to characterize the effect of the major refinery bases expected to be produced in the near future on pollutant emissions and on engine operation of the passenger cars and trucks which will be on the market during the next 20 years.The first of the three steps that constitute this program is based on an Euro 2 (1996) Renault Laguna 2.2 litres indirect injection diesel engine and a RVI truck Euro 2 engine. For the fuel formulation, an original approach is proposed: while the classical studies are based on the properties of the fuel, this one is built only on a refinery bases approach. Six refinery bases (a straight-run diesel fuel, a hydro-cracked diesel fuel, a LCO, a diesel fuel obtained by hydro-conversion of vacuum distillation residue, a kerosene and a diesel fuel issued from a Fischer-Tropsch process) have been selected to produce a fuel matrix which was determined according to an experimental blend design.The results led to the establishment of a relationship, which can be modeled as follows:specified pollutant emission = Σ αi Ciwhere,Ci is the concentration of the base i in the blend,αi is the contribution of the base i to the specified pollutant emission.Fuel refinery bases can be characterized by their contribution to engine emissions and they can be classified in four main groups: Bases which increase CO, HC, NOx and PM pollutant emissions (LCO and hydro-converted vacuum distillation residue); Bases which increase CO and HC emissions but decrease PM and NOx (kerosene, hydro-cracked products); Bases with intermediate contributions (straight-run and hydro-cracked products). Nevertheless, the hydro-cracked base is a minor contributor to HC, CO and CO2 emissions from the heavy duty engine; Bases which reduce all emissions (Fischer-Tropsch diesel fuel). The conclusions of this research study will aid the judicious choice of refinery components to reduce diesel vehicle emissions.