The results of the minimum miscibility pressure (MMP) determination for miscible injection of two gases (CO2 and an associated gas of one of Iranian gas reservoirs) into two different oil samples from two Iranian oil reservoirs using a slim tube apparatus are presented in this work. For efficient determination of MMP, prior to slim tube experimentation, cell-to-cell simulation of the slim tube experiment was performed using a tuned Peng Robinson equation of state as a pre-experiment and the results were used as initial estimates of MMP to select the pressure steps for the slim tube experiment. Finally, a comparison between the measured MMP values obtained by the slim tube experiments and those calculated by cell-to-cell simulation was made. It was shown that the cell-to-cell slim tube simulation predicts the results of slim tube experiments with a relative error of less than 6 %. This low error value shows that cell-to-cell simulation can replace the slim tube test in the cases where time is a major concern. Moreover, since the slim tube is an expensive and time-consuming experiment and selecting the pressures to run the test is very important, cell-to-cell simulation can help us select the pressures for performing a slim tube experiment.