To address the challenges of high energy consumption and elevated global warming potential (GWP) associated with refrigerants in -86 ℃ ultra-low temperature medical freezers, this study investigates a 568 L freezer employing a single-stage mixed-refrigerant J-T refrigerator. Two ternary hydrocarbon mixtures (R600a/R170/R1150 and R601a/R290/R1150) were experimentally evaluated as environmentally friendly alternatives to the conventional fluoride-containing mixture (R600a/R23/R14/R50). The refrigeration performance of the 2 hydrocarbon blends was analyzed without changing the system components; capillary, compressor and charge adjustments were made for R601a/R290/R1150 with the aim of reducing the refrigeration temperature, compressor discharge temperature and system energy consumption. Experimental results demonstrated that, without system modifications, R600a/R170/R1150 achieved a refrigeration temperature of approximately -60 ℃, whereas R601a/R290/R1150 attained -70 ℃. After reduction of the capillary tube inner diameter and replacement of the compressor with one suitable for R290, R601a/R290/R1150 achieved a refrigeration temperature of -87.3 ℃. Compared to R600a/R23/R14/R50, this configuration reduced the maximum discharge temperature by 11.4 ℃ and energy consumption by 32.9%. However, the pull-down time to -81 ℃ increased from 246 min to 404 min. Further adjustments by increasing compressor speed and refrigerant charge shortened the cooling time to 298 min while reducing energy consumption by 28.9%. These findings confirm that R601a/R290/R1150 not only achieves sub -86 ℃ refrigeration temperatures but also exhibits superior energy efficiency and environmental benefits. Therefore, this hydrocarbon mixture presents a viable eco-friendly alternative for ultra-low temperature freezer applications.