The gaseous pvTx properties of CO2 (1, CAS No. 124-38-9) + propane (2, CAS No. 74-98-6) mixtures were measured using the Burnett-isochoric method with 225 data points obtained for temperatures from (320 to 400) K, pressures up to 7784 kPa, and densities up to 141 kg·m−3 at x1 = 0.5158 and x1 = 0.8017. Burnett measurements for argon (CAS No. 7440-37-1) were conducted at 319 K and for CO2 at 343 K. The pvT properties and virial coefficients of argon and CO2 agreed well with literature results when the effective cell constant for each fluid instead of that of the helium calibration was used in the density calculations. The temperature, pressure, density, and mole fraction uncertainties were estimated to be ± 5 mK, ± 300 Pa, ± 0.05 %, and ± 0.01 %, respectively. A truncated virial equation was used to correlate the experimental pvTx data of CO2 + propane mixtures with root-mean-square deviations of ± 0.03 %. The second and third virial coefficients for the binary mixtures were also determined.