How does FR3 transformer oil compare to mineral oil in thermal aging performance?

In many service conditions, FR3 can improve thermal aging behavior of paper insulation because esters tend to reduce paper moisture over time, and lower paper moisture slows depolymerization. FR3 also offers strong oxidation stability in sealed systems and supports high temperature operation depending on design. Mineral oil typically has excellent low temperature viscosity and is widely proven, but it does not manage paper moisture the same way. Actual aging performance depends on sealing, oxygen exposure, temperature profile, and maintenance practices, so fleet specific evaluation matters.