A method of monitoring performance of an auxiliary pump is provided. A monitoring system measures a first pressure at a location supplied by a main pump and the auxiliary pump while the auxiliary pump is operated at a first speed. The monitoring system measures a second pressure at the location while the auxiliary pump is operated at a second speed. The monitoring system calculates performance of the auxiliary pump based on a difference between the first pressure and the second pressure divided by a difference between the first speed and the second speed. The monitoring system tracks the performance of the auxiliary pump over time by repeating the measuring and calculating over time.