In accordance to the current environmental policy of the European Union by 2020, 10% of the transport fuel in every country comes from renewable sources such as biofuels. One of the most popular biofuels, (bio) ethanol is a probable suitable candidate for addition in diesel fuel because of its cleaner combustion and the ability to reduce emissions of gaseous pollutants. However, its use presents some important problems, attributed mainly to its incompatibility with diesel fuel during mixing due to the difference in the polarity. For this reason, substances that act as stabilizers of these mixtures are used, one of the most suitable being butanol. This substance is compatible with diesel fuel and ethanol, acting as a chemical bridge between the two, but also exhibits positive combustion behavior, as it is also an oxygenate that can be produced from renewable sources as well. The aim of this work was to investigate the behavior of diesel-ethanol mixtures using butanol as co-solvent. Different ultra low sulfur diesel (ULSD) samples, as well as a renewable paraffinic fuel derived from hydrotreatment of vegetable oils (HVO) were used as base fuels for the preparation of diesel - ethanol blends, with the addition of n-butanol as co-solvent. The main idea was to produce stable blends that can be used as fuel in diesel engines. The results showed that the production of stable diesel - bioethanol - butanol ternary blends is feasible. The amount of butanol that is required depends on the composition of the main fuel, with the aromatic content of the base fuel to be a critical parameter. Oxidation stability of the stable ternary blends was also evaluated in a Rapid Small Scale Oxidation Test unit, while other properties, such as ignition quality, were also measured. The results showed that the addition of the two oxygenates affect the oxidative characteristics of the base fuel, whereas a decrease in cetane number was observed.