Biodiesel is an alternative fuel derived from vegetable oils, animal fats and used frying oils. Due to its chemical structure, it is more susceptible to oxidation or autoxidation during long-term storage compared to petroleum diesel fuel. One of the major technical issues regarding the biodiesel blends with diesel fuel is the oxidation stability of the final blend, which is, nowadays, of particularly high concern due to the introduction of ultra low sulphur diesel, in most parts of the EU. This study examined the factors influencing the stability of several biodiesel blends with low and ultra low sulphur automotive diesel fuels. The aim of this paper was to evaluate the impact of biodiesel source material and biodiesel concentration in diesel fuel, on the stability of the final blend. Moreover, the effects of certain characteristics of the base diesels, such as sulphur content and the presence of cracked stocks, on the oxidation stability are discussed. (C) 2010 Elsevier Ltd. All rights reserved.