The aircraft engine lube oil filter maintenance practices of a small commercial airline were studied. Engines with known Times Since Overhaul (TSO) were selected and operating hours on the filters were controlled at 50 and 100 hours. The differences in filter pressure drops and particle contamination levels were recorded and a spectrometric analysis was performed on an oil sample from each oil change. The practices evaluated are satisfactory for both the 50 and 100 hours filter periods. The oil spectrometric analyses showed little oil degradation and no relationship between TSO and the recorded data could be obtained.