 The study investigates the mutual diffusion of six hydrocarbons in supercritical carbon dioxide near the Widem line and provides an experimental database with thick diffusion coefficient data for those systems. Taylor dispersion experiments are conducted to analyze Maxwell-Stefan and thick diffusion coefficients, as well as the thermodynamic factor that relates them. It is found that the peculiar behavior of the thick diffusion coefficient in SUM485804 CO2485804 CO2 mixtures in the extended critical region is due to pronounced clustering on the molecular scale. The study also confirms the strong dependence of the thick diffusion coefficient on the molecular mass of the solute and the breakdown of the Stokes-Einstein relation near the Widem line. 11 correlations for predicting the thick diffusion coefficient of 485804 backslash H-box CO underscore 2 485804 CO2 mixtures are assessed, and a two-step approach is proposed for predicting the infinite dilution thick diffusion coefficient of supercritical 485804 backslash H-box CO underscore 2 485804 CO2 mixtures based on temperature, pressure, or density and molecular solute mass as input parameters. This article was authored by Dennis Sarek, Gabriella Gavaracharian, Yuri Gapanenko, and others. We are article.tv, links in the description below.