Oxidation stability tests evaluate how resistant the oil is to forming acids, sludge, and polar compounds under heat and oxygen exposure. Poor oxidation stability can lead to rapid acidity increase, lower interfacial tension, higher tan delta, and deposits that restrict oil flow and cooling. That cascade raises hot spot temperatures and accelerates paper aging. Utilities use oxidation stability to qualify new oils, compare inhibited versus uninhibited products, and decide whether regeneration or replacement is needed. It is especially important for long life assets where oil is expected to perform for decades under varying loading and ambient conditions.
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