According to the results of several studies concerning the influence of fuel formulation on exhaust emissions from diesel engines, a new matrix of twelve fuels was tested in a single cylinder DI diesel engine of conventional technology.The matrix was designed by the partners of the FLOLEV research project, partly founded by the E.U., in the framework JOULE III program.The aim of the project is to study the influence on pollutants emission reduction of modern refining process and fuel additivation with some alternative fuels and cetane improvers.The fuel matrix is structured into three sub-matrices. The first sub-matrix is constituted by six fuels which represent different products obtainable with the modern refinery technology. The second and third sub-matrices were designed to test the influence of cetane improver additives and high-oxygenated fuels respectively.The single-cylinder engine of 0.75 Liter of displacement, equipped with a cooled E.G.R. laboratory system, was selected because of its high “sensitivity” to the fuel quality changes.The in-cylinder combustion behavior of twelve fuels was followed with the two-colour pyrometry technique and the fast sampling valve technique. The exhaust gaseous emission, as well as particulate and aldehydes emission, were measured.Taking into account the influence of different fuel parameters (cetane number, aromatics, sulfur etc.) on pollutants emission, the behavior of the six base fuels, and then the potentiality of the relative refining process, can be explained.