A model predicting 12 properties of diesel-biodiesel mixtures was developed. This was based on existing correlations capable of providing quality characteristics for the mixtures. The model was also used to maximize the biodiesel fraction in the diesel-biodiesel mixtures, while taking into consideration all product quality specifications as they are defined by Greek Legislation. The properties examined were ;density, viscosity, cloud point, pour point, volatility at temperatures 250 degrees C, 350 degrees C and 360 degrees C, cetane index, cetane number, sulfur, water, higher heating value, flash point and cold filter plugging point (CFPP). The model was evaluated for mixtures between two diesel types (normal diesel and Shell extra diesel) and four biodiesel types (i.e. biodiesel produced from different vegetable oils). The model was developed in MATLAB and the corresponding biodiesel optimization studies were carried out with the MATLAB's optimization toolbox. (C) 2011 Elsevier Ltd. All rights reserved.