does not have a sensor to tell you when the oil should be changed. That came in later models of the E class. I would change the oil right away since you probably don't know what kind of oil was in it when you got it. Unless the car has had synthetic oil used in it in the past, I would use a good quality 5W30 natural oil with new quality filter every 4000-5000 miles but at least twice per year. This is what I do for my 1997 E320 and it just crossed 125,000 miles and doesn't use any oil between changes.