This paper presents the results of an experimental study on the synergistic effect under the combined action of CO2 corrosion and abrasive wear on low-alloy steel 09G2S, commonly used in oil and gas pipelines. The study was conducted using a specialized flow-loop test bench simulating real operational conditions, including flow velocity (up to 5 m/s), CO2 concentration (1.2 g/L) and abrasive particles (SiO2 sand, 4.2 g/L). The material degradation rates were evaluated using gravimetric and electrochemical (LPR) methods. The results demonstrated that under the combined action of corrosion and erosion, the total mass loss (4.7634 mm/year) significantly exceeded the sum of individual corrosion (1.7495 mm/year) and erosion (1.6821 mm/year) losses, confirming the presence of the synergistic effect. The calculated synergy coefficient (2.8671 mm/year) and factor contribution analysis revealed dominant synergistic interaction (60% of total degradation), while pure erosion and corrosion accounted for 27% and 13%, respectively. The ΔCR/ΔER ratio of 0.117 (according to ASTM G119-09) corresponds to the equality of synergistic and additive effects with a shift towards synergy. The obtained data are of practical importance for predicting pipeline service life and developing protection methods against corrosion-erosion wear. The proposed methodology combines field-representative conditions with high measurement accuracy.