In this work, the extended Lennard-Jones potential-based equation of state (ELJ-based EoS) on which the effective near-neighbor pair interactions are LJ (12,6,3) type has been extended to predict the density and other thermodynamic properties of hydrocarbons up to extremely high temperature, high pressure (HTHP) conditions. It seems that, at least in the dense regions, there are no upper and lower density limitations in the applicability of the model for different hydrocarbon systems. Having the temperature dependence of the parameters of new EoS, the parameters can be determined at any temperature for each of 38 studied compounds, including short- and long-chain alkanes ranging from CH4 to n-C40H82, and also several cycloalkanes, highly branched alkanes and aromatic hydrocarbons. The calculated parameters have been used to calculate the density and other derived thermodynamic properties of different hydrocarbons at any temperature and pressure. The results show that EL-based EoS is clearly superior to those obtained using previous works in accord with experimental data up to HTHP conditions. (C) 2012 Elsevier B.V. All rights reserved.