A new mixture model, explicit in the reduced Helmholtz energy, is proposed for modeling the thermodynamic properties and phase equilibria of technological oil fractions. The model covers a broad temperature and pressure range in gaseous, liquid, and supercritical regions. Based on the given hydrocarbon composition, a complex mixture is modeled by individual substances, which are identified by the acentric factor and critical parameters, while calculations of thermodynamic properties are carried out with use of individual and generalized equations of state. The generalized equation of state for normal alkanes has been used to describe the thermodynamic properties of a seven-component mixture for which there are no individual equations of state. To improve the description of the thermodynamic properties, the binary interaction parameters for ten binary systems were adjusted. The fitting procedure is based on a cubic equation of state with the group contribution and the evolutionary optimization algorithm. The results of comparison with the experimental data on density, isobaric heat capacity, enthalpy and entropy of vaporization are presented. The comparison was performed over a temperature range 300-630 K and pressures up to 60 MPa excluding the critical region. The average absolute deviations of the properties from optimized values are the following: 0.17% for the liquid-phase density; 3.5% for the gas-phase density; 2.2% for the density in the supercritical region. The average absolute deviation of isobaric heat capacity for the liquid phase is 1.5-3.5%, for the gas phase is 2.5%, in the supercritical region is 2.1%. The average absolute deviations of the vaporization enthalpy and entropy are 1.65% and 2.23%, correspondingly.