I bought the car when it had exactly 100k on it. I immediately changed the oil in it to Mobil synthetic. My experience with Mobil synthetic is that you can typically go a bit longer on oil changes than with regular oil. I have made a practice of changing it between 5k-6k. I have checked with my local MB dealer and they recommend with synthetic oil changes at 7500 miles. The car does not seem to use a drop of oil in between changes.