Just had the dealer change the oil for the first time at 4,000 miles on my 2008 Dodge Sprinter 3500 Diesel. After just ten miles, is the oil supposed to look dirty?....not real black more like a gray color. I'm wondering if the dealer actually changed the oil. In all the gas engines I've had, the oil would look like it just came out of the bottle. This is my first diesel and my first Sprinter. Thanks for any answers.