Existing method for determining the transport properties in the rarefied gas and binary gas mixtures are reviewed and their deficiencies are discussed. Emphasis is placed on research of transport prop-erties of the new low GWP potential warming synthetic fluid R1234yf and CO2 + R1234yf binary mix-ture in ideal gas state. A theoretically based correlation scheme employing the Mason–Monchick–Parker formalism has been examined and found to be useful as correlation and prediction schemes for thermal conductivity calculations in the limit zero density for dilute gas of 2.3.3.3-tetrafluoropropene. The thermal conductivity of gaseous mixtures CO2+R1234yf at low pressures was defined by a variation of the Lindsay–Bromley relation based on the Wassiliewa–type equation devel-oped for mixtures with large difference in molecular size. Some results are described to show how the calculations have judgment in studies of the transport properties data. Comparisons with limited amount of experimental information available indicate that the procedure allows evaluation of the transport properties of gas mixture to with a few percent.