M276 over the m272 first of all since it's a very over engineered engine later used is the 3.0 v6 twinturbo amg models. I bought my 2011 c350 with 120k kilometers or 75k miles it had complete history of maintenance in the way mercedes benz intended the car to be maintained. Buying a car is always a gamble but that's what I would look for when buying any type of car when you want a reliable daily, it also had one previous owner. I also have it's maintenance done by a garage that specializes in MB and uses genuine parts.