The research examines the ageing behavior of piezoelectric pressure sensors for internal combustion engine studies while concentrating on their declining sensitivity as time progresses. Reliable measurement of in-cylinder pressure demands precise monitoring of sensor performance to support both thermodynamic analysis and evaluation of engine performance. Research experiments performed with a single-cylinder research engine (SCRE) determine how the working cycle operational parameters relate to sensor properties, especially the indicated mean effective pressure (IMEP) and polytropic coefficients of the compression/expansion phase of the engine working process. The study demonstrates that monitoring polytropic coefficients provides an efficient technique for detecting sensitivity degradation without needing continuous pressure sensor recalibration, improving both accuracy and efficiency during prolonged engine testing. The approach allows researchers to detect sensor degradation on time, which helps maintain data integrity throughout lengthy research campaigns.