If you need an oil change will your check engine light come on?

No, a needed oil change will not cause the check engine light to come on. The check engine light illuminates when the car's onboard diagnostic system (OBD-II) detects a problem with the engine or emission system. Low oil pressure is a serious issue that *can* trigger the check engine light, but the light will not come on simply because the oil is old and needs changing. You might get a low oil pressure warning light in that extreme situation, however.