Ethane contamination poses significant challenges to the operation of C3MR cooling cycles and LNG production. This study investigates the impact of ethane contamination on the propane pre-cooling cycle of the GL2/Z plant (Arzew-Algeria), quantifying its economic, environmental, and technological implications. The propane cycle was simulated using ASPEN-HYSYS v12 software, with results showing good agreement with operating data. The study reveals that ethane levels in propane must not exceed 2% molar composition, as above 6 mol% of ethane in propane, the contaminated propane is flared. In April 2024, 1455.6 tons of propane was lost, totaling approximately $582,240. Through simulation and analysis, we predict the behavior of the propane cycle under progressive ethane contamination and identify potential adjustments to protect critical equipment. Results indicate that ethane contamination leads to malfunctions in the propane cycle, affecting the performance of the MR cycle. Significant issues, such as ethane leaks from specific exchangers, cause the flaring of propane. Quantifying the economic repercussions reveals substantial financial burdens associated with ethane contamination, including increased electricity consumption and costs related to flaring contaminated propane Moreover, the downstream effects beyond the propane pre-cooling loop, causing disruptions in the entire LNG liquefaction process due to elevated temperatures, underscore the need for comprehensive mitigation strategies. This study highlights the complex and multifaceted nature of ethane contamination's impact on C3MR cooling cycles, emphasizing the importance of effective monitoring and mitigation measures for continued operational efficiency and profitability in LNG production facilities.