What kind of gas does mercedes c300 take?

All Mercedes Benz vehicles, including the C300, are recommended to use premium unleaded gasoline with an octane of 91 or higher. While this isn't necessarily required, it's STRONGLY recommended. The engines were designed with premium in mind, so using a lower octane gasoline can cause issues for You, especially over the long term. While You may save at the pump, You'll pay out for repairs over the long term. Lower octane gasoline has a good chance of causing engine knocking in vehicles that were designed for higher octanes. Over the extremely short term, this is more of an annoyance than anything. However, once engine knocking begins, so does the damage to Your engine components. If You're runninG87 oR89 for an extended period, the knocking will eventually cause damage, and perhaps even failure.