Material aging and structural deformation are two closely connected failure modes of oil seals used in high-temperature hydraulic systems. As heat acts on the elastomer over time, the rubber compound gradually loses flexibility, resilience, and dimensional stability. This process may include hardening, embrittlement, thermal oxidation, and permanent compression set. Once the material properties change, the oil seal can no longer maintain uniform contact at the shaft interface. Structural deformation then develops in the form of lip distortion, body warping, and reduced spring-assisted sealing force. These issues are often intensified by high shaft speed, pressure fluctuation, poor lubrication, and contamination. In practical hydraulic equipment, failure of the shaft oil seal may lead to oil leakage, pressure instability, increased wear, and expensive downtime. Material selection therefore plays a decisive role in performance under heat. Industrial seals manufactured with enhanced temperature resistance and accurate structural design help reduce these risks. They support long-term sealing stability in hydraulic pumps, motors, reducers, and other rotary systems used in heavy machinery, industrial automation, engineering equipment, and power transmission applications where reliable operation under elevated temperature is essential.