In this work, the performance of the UMR-PRU model, which combines the Peng-Robinson (PR) equation of state (EoS) with the original UNIFAC through the Universal Mixing Rules (UMR), is further improved and updated through the use of a Mathias-Copeman (MC) function for the attractive term parameter of the PR EoS. The new model, called UMR-MCPRU, utilizes a newly parametrized MC function for the a term, which satisfies consistency constraints that ensure its safe extrapolation to the supercritical region. Moreover, a correlation of the MC parameters of hydrocarbons with acentric factor is proposed. The MCPR EoS is then combined with the UMR mixing rules, resulting to the UMR-MCPRU model. All binary interaction parameters relevant to natural gas mixtures are determined by fitting binary vapor-liquid equilibrium data. UMR-MCPRU is used to predict vapor-liquid equilibrium, critical points, liquid dropouts, densities (rho) and derivative thermodynamic properties, namely isobaric (c(p)) and isochoric (c(V)) heat capacity, Joule-Thomson coefficients (mu(JT)) and speed of sound (w), of natural gas and gas condensate mixtures. The Peneloux volume translation is also examined, wherever relevant. The results reveal that UMR-MCPRU, coupled with the Peneloux translation, is able to accurately describe both phase equilibria and other important thermodynamic properties of natural gas and gas condensate mixtures.