This study investigates the temperature dependence of vibrational relaxation for the asymmetric CO stretching mode of W(CO)6 in supercritical ethane and carbon dioxide. The experimental data, collected using infrared vibrational pump-probe techniques, are compared with theoretical predictions from an extended hydrodynamic theory. The theory, which incorporates detailed solvent properties, successfully reproduces the observed behavior without free parameters. Specifically, it captures the inverted temperature dependence observed in ethane at the critical density, where the vibrational lifetime initially increases and then decreases with further temperature increases. In contrast, at high densities in ethane and in CO2, the inverted temperature dependence is not observed, which is consistent with theoretical calculations. The study highlights the importance of solvent properties and the role of critical phenomena in understanding vibrational relaxation in supercritical fluids.This study investigates the temperature dependence of vibrational relaxation for the asymmetric CO stretching mode of W(CO)6 in supercritical ethane and carbon dioxide. The experimental data, collected using infrared vibrational pump-probe techniques, are compared with theoretical predictions from an extended hydrodynamic theory. The theory, which incorporates detailed solvent properties, successfully reproduces the observed behavior without free parameters. Specifically, it captures the inverted temperature dependence observed in ethane at the critical density, where the vibrational lifetime initially increases and then decreases with further temperature increases. In contrast, at high densities in ethane and in CO2, the inverted temperature dependence is not observed, which is consistent with theoretical calculations. The study highlights the importance of solvent properties and the role of critical phenomena in understanding vibrational relaxation in supercritical fluids.