A three-parameter cubic equation of state for pure hydrocarbons is proposed to model PVT properties of heavy hydrocarbons found in heavy oils. Thirty hydrocarbons up to C40 and some commonly found (associated) non-hydrocarbons in heavy oils have been used to regress the parameters. Predicted results from the proposed equation for the liquid density, vapour pressure, saturated liquid density, and saturated vapour density have been compared with the widely used Peng-Robinson (PR), Soave-Redlich-Kwong (SRK), and Patel and Teja (PT) equations of state. With the increase in carbon number in hydrocarbon, the % average absolute errors in liquid density, vapour pressure, and saturated liquid density prediction using PR, SRK, and PT equations of state were found to increase, whereas the proposed equation shows consistency in the prediction, with a % average absolute error of 2.5% only.