To reset the 2004 Mercury Monterey oil life, please follow these instructions:

1. Turn the ignition to run (one position before starting engine).
2. Press the STATUS control to access the System Check function.
3. Press RESET to reset oil %.
4. Press and hold the RESET control to set to 100%. After a successful reset, the message centre will display OIL LIFE SET TO 100%.
5. Turn the ignition off and then start the engine to verify the indicator has been reset.