on the dash there should be three buttons info, setup and reset one of those you press a few times and should show reset oil
First turn the key to the run position (dash lights on and gauges on) you do not have to start the car. Now look for the "info" button. Push the info button until you see "push set for system check". Then push the "set" button After you push "set" you will see the oil life setting. Mine was at 0% life remaining. Now push the "set" button for 5 to 10 seconds until you hear a beep. Then the oil life will show 100%. Start the car and the oil change warning should be off. If not just retry the procedure. Where i made my mistake was in not holding the set button down long enough. Both the info and set button are in the center of the dash near the radio.
By resting it on the computer manually
Bing it.
On the "Information" panel on the dash press the "set-up" button 6 times. The message on the Information panel will read "Oil Life Set to XXX %." Press and hold the "Reset" button. The message will disappear.
Read the Manual
Disconnect the negative side of the battery
To reset the service engine soon light on a 2006 Mercury Mountaineer, you can buy a scan tool. Make sure you note down the numbers before scanning.
Follow prcedure in manual to re-set--probably was not reset last time oil was changed maintain proper oil level and when it is changed be sure to reset light so it will be in "cycle"
In the front passenger footwell , behind the kick panel
Try disconecting the battery for 5 min.s and reconecting.
In the front passenger footwell , by the kick panel
It should be in the right front passenger footwell , by the kick panel ( that's where it is on a Ford Explorer ) O.K. you got me ! - I forgot that the Mercury Mountaineer started with the 1997 model year
According to the 2001 Mercury Mountaineer owners manual : The fuel pump shut off switch ( inertia switch ) is in the front passenger footwell , by the kick panel