I know this sounds silly, but does the car have a dip stick? Just because the light came on doesn't mean it is low on oil. It could be the oil level sensor. Possible the engine is over filled. My 2005 C320 does not have a dip stick. The light, really a message, came on. I took it to the dealer and they have a universal dipstick and confirmed the car had the correct level and the oil sensor was bad.