To reset the 2003 Mercury Mountaineer oil life, please follow these instructions:
1. Turn the ignition to run (one position before starting engine). 2. Press the SETUP control to access the System Check function. 3. Press and release the RESET control to display “OIL LIFE XX% HOLD RESET NEW”. 4. Press and hold the RESET control for 2 seconds to display “IF NEW OIL HOLD RESET”. 5. Press and hold the RESET control to display “OIL LIFE SET TO 100%”. Your oil life is now reset. 6. Turn the ignition off and then start the engine to verify the indicator has been reset.