The vehicle's computors determine by your driving habits and by temp, lenght of drive's, etc. when you should have your oil changed. It doesn't mean you have to have your oil changed but it recommends it. You can reset the light by turning the ignition to on and pressing the accelerator to the floor 3 times in ten seconds and then turning the ignition to off. That will reset the counter to 0 and it will illuminate the next time it thinks you need an oil change.