Presents a field study to demonstrate the performance of a gas-engine cooling system using R134 in an actual cooling application. Monitors the performance of two similar gas-engine systems installed in the same application but using two different refrigerants, R22 and R134a. Determines their energy use, delivered cooling capacity and efficiency as well as hours and modes of operation. Presents the findings. Concludes that a system with R134a performed with an efficiency similar to a comparable system using R22 and that R134a could be practically used in a field-erected gas-engine cooling system. Calculates that overall, the gas-engine cooling system saved nearly $6000 a year in operating costs in Brooklyn, N.Y. compared to a hypothetical, all-electric system.