In the Waste Heat Recovery industry, thermal fluids play a critical role in capturing, transporting, and reusing residual energy from exhaust gases, reactors, ovens, thermal oxidizers, and process loops. A well-designed heat transfer system helps plants convert wasted thermal energy into useful heating or integrated utility support, improving energy efficiency, lowering fuel demand, and reducing overall operating cost. In these applications, fluid stability, viscosity, and controllable circulation are essential for safe long-term service. EuroTherm 320 (E320)offers a-30 to 320°C operating range with 9.8 mm²/s viscosity at 40°C, combining low kinematic viscosity, strong thermal stability, and high cost-effectiveness for standard recovery loops and indirect heating networks. EuroTherm THT (THT) extends performance to -10 to 350°C with 28 mm²/s viscosity at 40°C, making it well suited to higher-temperature recovery duties where low system pressure and long-term thermal durability are priorities. For plants that require broader utility flexibility, XT-1,XT-2,XT-3, andXT-4 can be positioned in auxiliary cooling, cold-end stabilization, start-up/shutdown control, and integrated heating-cooling sections of the recovery system, helping smooth thermal transitions and improve overall process responsiveness. Together, E320 / THT / XT-1 / XT-2 / XT-3 / XT-4 support safer operation, better energy reuse, and more reliable continuous performance in modern waste heat recovery facilities.