Trying to find the recommended oil for my car is like going through a maze. Car is a 308 1.6 hdi 90, 2009. Was told by local supplier it was Castrol magnatec 5/30 synthetic. Since putting it in the engine has developed a rattle when cold from cam area. Could it be the wrong oil or just coincidence? What oil does Peugeot recommend? If I need to change the oil is it worth while putting a decent engine flush through first? Should take the old oil back and make him drink it?