The "Oil" warning light refers to low oil pressure, not level. If you are lucky, the sending unit may be defective. The oil pressure will go down at lower engine speeds. Forty pounds is normal. Most warning lights turn on at around ten pounds.
There are two other common causes of this symptom. The oil gets thinner when it is hot so it is easier to run out of the engine bearings. That makes it harder to keep the pressure up when the engine is pumping it at a low volume at low speeds.
The other cause is worn engine bearings. At the mileage you listed that really should not be a problem yet. If the problem persists after the oil change, your mechanic can check the actual pressure with a mechanical gauge.
Wednesday, July 20th, 2016 AT 9:42 PM