The complicated nature of asphaltene molecules besides the unknown mechanism of phase separation of asphaltene-containing systems as well as lack of a suitable characterization parameter has questioned the generality of the available thermodynamic models. The scaling equation developed by Rassamdana et al. [10, 13] and its generalized form presented by Hu et al. [20] proved existence of a general relationship to model the asphaltene precipitation envelope and the onset. However, it works only for dead oil systems: here it has been tried to extend this technique for live oil fluids at reservoir condition. In this study, three types of experiments were conducted on five live reservoir fluid samples. The samples were collected from a giant Iranian oil field to measure the amount of precipitated asphaltene for a wide range of temperature and pressure. The results of this study developed a new live oil scaling equation and successfully applied to predict a new real data-set. The predictions of the model were compared with the two widely used thermodynamic methods of single component solid and modified Flory-Huggins (FH) models. The results show that the phase stability and the regions where asphaltene precipitates from the live crude oil were predicted using this new scaling equation with an acceptable accuracy. (c) 2012 Elsevier B.V. All rights reserved.