I have become the proud owner of a 2011 Kia Optima. I love the interior and exterior of the car. I can't say that about a few cars that I have purchased over the years. It is a 2.4 liter direct injection engine. From what I have read, these engines are more stressful on engine oil. Would a synthetic oil be in order here? The maintenance schedule says to change the oil every 5000 kilometers. I will do this during warranty period. What would you do?