TOR-5 is not limited to mineral oil only – in principle it can also be used with synthetic and natural ester fluids, but with some important considerations. The main difference is that esters have much higher water solubility and different moisture equilibrium behavior, so sensor calibration and alarm thresholds must be adapted. Moisture in ppm has a very different meaning in esters than in mineral oil. Hydrogen and temperature monitoring work the same way, but interpretation of trends must follow ester-specific standards. So the system is suitable, but it requires proper configuration and different diagnostic criteria.