Recommendations for Getting an Accurate Oil Reading

Q: Recently, I checked my car’s engine oil level while refueling at a self-service gas station, which is something I never do. I was somewhat worried when I discovered it was almost a quart low. But the next morning, I checked again, and the oil level was normal. Why would there be this difference?

A: Most likely, nearly a quart of oil was in the engine’s oil passages and upper cylinder head area and had not returned to the engine’s oil pan when you took your first reading. Some automakers recommend that you wait up to 20 minutes after shutting the engine off before checking the oil level to avoid this problem. Your car’s owner’s manual will outline the proper procedure for your model.

In many vehicles, the best time to take an oil reading is after the car has been parked overnight on a level surface and the engine is cold. Some automakers, however, recommend checking the oil level on a warm engine. After taking the reading, be sure to properly seat the dipstick in its tube.