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A set of additives was selected to improve the durability of the physical-chemical and biological characteristics of mineral diesel and its blend with biodiesel. Two biodiesels were used: soybean (SME) and rapeseed (RME). Both physical-chemical properties and fuel dispersion of fuel blends and their mixtures with additives were measured that could have effects on the combustion process in diesel engines. The dispersion of the fuel is affected by the injection nozzle integrity, influencing the capacity of the fuel to vaporize, while the modification of the fuel molecular structure can cause changes in combustion reaction. A 7 hole Common Rail (CR) 2nd generation injector, 136 ?m in diameter, was used at 80 MPa and 1.0 ms injection pressure and duration, respectively. The injection rate was determined using the Bosch's Method, while the fuel dispersion was measured by analyzing the images of spray evolving in an optical accessible quiescent vessel. The results showed that the additives have a great influence on the stability of the blends. Adding the biocide "P", antioxidant "AN" and pour point depressant "D", an increase of the oxidation stability of 390 % of the B20SME samples compared to B20 without additives. For B20SME containing "P", "AS" and "D", the oxidation stability increased of 810%. The injection rate data showed that a slight reduction in the rate of injections (9.91% for Diesel B5RME, 8.13% relative to B20RME and 12.84% relative to B20SME) was registered when additives were used. Finally, the inclusion of the additives did not produce particular variations on the fuel spray tip penetration.