A new, unified, phenomenological, simple, molecular theory of transport properties is presented and applied to hydrocarbon compounds. A Pressure-Temperature (P,T) ensemble has been used to describe the transport properties of viscosity, thermal conductivity and self-diffusion coefficient. The application of the theory to many hydrocarbon compounds is illustrated in many tables. The low density limits of viscosity and thermal conductivity are examined to find a linear relation with the square root of the absolute temperature. The case of self-diffusion coefficient is somewhat different because the high density limit (low limit of empty sites) is linear related to the square root of absolute temperature. The high density limit of viscosity coincides with the Batschinski-Hildebrand empirical equation. The connection of the present theory to the Sanchez-Lacombe equation of state parameters is well established, which leads to a molecular interpretation of the theory. The application of this theory to binary mixtures is also illustrated with different tables. Finally, some important conclusions are drawn.