Oil level gauges show whether the tank and conservator contain sufficient oil for insulation coverage and cooling circulation. Low level can expose windings, increase partial discharge risk, reduce cooling, and allow air ingress that accelerates oxidation. High level may indicate overfilling or abnormal expansion behavior. Many gauges include temperature compensation and alarm contacts for low and high levels to support SCADA monitoring. Accurate level indication is critical after maintenance, after temperature swings, and during leak management to prevent overheating and insulation damage.