Most times your vehicles CHECK OIL LIGHT will come on -on your dash.  When this happens, it's usually time to take your vehicle into a shop and have your oil changed.  It's also wise to check your fluids before heading out on a long trip. If you're not sure how to check your oil or other fluids, this video will explain and show you how. Click on the video link below. http://www.youtube.com/watch?v=eogAlc3LR4w