An automatic engine stop-start system of a vehicle having an engine includes a controller in signal communication with the engine and configured to command automatically stopping and starting the vehicle engine, a first sensor in signal communication with the controller and configured to generate a first signal indicative of a grade of a road the vehicle is located on, and a master brake cylinder having a pressure sensor in signal communication with the controller, the pressure sensor configured to generate a pressure signal indicative of a master cylinder brake pressure. The controller is further configured to determine a pressure threshold based on the first signal and the pressure signal. When the pressure signal exceeds the pressure threshold, thereby indicating a driver is releasing a brake pedal of the vehicle, the controller commands automatically restarting the vehicle engine.