In order to develop a method for assessing the service life, the values of kinematic viscosity at temperatures of 100 °C and minus 40 °C, acid number and amount of sediment insoluble in isooctane, critical load and the wear scar diameter, height and time of destruction of the foam column, as well as the tensile strength of IRP-1316, IRP-1287 and 51-1434 sealing rubbers of aviation oils were determined in the state of delivery and after oxidation at temperatures of 200, 225, and 240 °C. The influence of water in concentrations of 0.01, 0.1 and 1% on the performance properties of oils, was estimated. Based on the mathematical dependences obtained for the property values on the time and temperature of oxidation, the estimation of the operating time of the standard oil for aircraft gas turbine engines and helicopter gearboxes was carried out