A method of determining lubrication oil consumption in a gas turbine engine that has an engine operating cycle interval comprising a starting phase, a running phase and a shutdown phase, comprises the steps of: measuring lubrication oil level upon initialization of the starting phase of each engine operating cycle interval; comparing the starting phase measured lubrication oil level during the starting phase with a starting phase baseline lubrication measurement; recording the starting phase lubrication oil level measurement; determining average engine lubrication oil consumption rate during the complete engine operating cycle interval by dividing the difference between the starting phase lubrication oil measurement and the baseline lubrication oil measurement; and repeating these steps for each subsequent engine operating cycle interval; wherein the starting phase baseline lubrication oil level measurement is initially a predetermined lubrication oil level and then the previous starting phase lubrication oil measurement for subsequent engine operating cycle intervals.