ALT-1 What to do when your Oil Light comes on
Contrary to popular belief, the engine oil light indicator does not have any sensors that monitor the amount or condition of the oil in your vehicle. Many times people see the oil light on, and automatically assume it is time for an oil change. This can often be an incorrect assumption.
The oil light actually works on math models developed by the manufacturer which factor in miles driven since you last reset the oil light. If you change your oil without reseting the oil light, its sensors fully believes that the oil has not been changed at all, therefore the oil light itself might come on weeks or even days later, though your car is full of new oil.
Nevertheless, it is always better to be safe than sorry.
If your oil light comes on the first thing you need to do is pull over and check your oil. Remember that the oil system is pressurized, so you cannot get an accurate reading on your oil dipstick if the car is running. If no oil shows up on your dipstick, it is also important to note that the oil dipstick itself only measures the top quart of oil. In other words, it is possible for a vehicle to only be one quart low on oil and for the vehicle's oil dipstick to be completely dry. If there is no oil on the dipstick, you should add oil one quart at a time, checking the dipstick in between.
If there is oil on the dipstick, and if you can safely look under the car, try and locate the oil pan and filter, and check them for leaks. If the oil is full, and there are no oil leaks, you probably just need to reset the oil light, although, unless you are very knowledgeable about engines, it's best to bring your car to a mechanic or oil change shop as soon as you can so that a trained professional can make the ultimate diagnosis.
The oil light can also go off for a variety of other reasons, such as faulty sensors. Always physically reaffirm that there is oil in your vehicle, preferably right when the oil light comes on, or as soon as possible afterwards. You should never run a vehicle that is low on oil, as this can seriously damage your engine relatively quickly. If the oil is full and you are reasonably sure the oil isn't leaking, drive your vehicle to the nearest mechanic shop or dealership and let them have a second look. Most places will not charge you for reseting the oil light.
