The main obstacle in biodiesel/conventional diesel blends acceptance worldwide seems to be its poor oxidative stability. Low resistance towards oxygenation is due to the fatty constituent in the blend. Even low concentrations of biodiesel (5%, 10% and 20%) can contribute to sticky, viscous and polymeric deposits formation after several months of storage. Two correlations were derived concerning insolubles formed in both stabilized and not stabilized blends, stressed under conditions of ASTM D2274. For treated with antioxidant additive: Total insol. = 0.6561 + 80.1213 * Delta TAN - 114.27 * Delta PC - 2.6073 * Delta IV For not stabilized samples: Total insol. = -229.348338 - 13.2360978 * Delta TAN + 968.531862 * Delta Visc. - 25.0335999 * Delta IV The correlations' precision is described by the high value of R(2) = 1.0000. Present work proves that it is possible to stabilize such a blend even the fatty component is aged for a period of three months. (C) 2008 Elsevier Ltd. All rights reserved.