Yeah, why does Corvette factory fill with Mobil 1 5w30? A guy I work with has a C5 ls1 and he uses Mobil 1 and dosen't burn any??? I hear all Porshas(sorry spelling)and Vipers are factory filled with Mobil 1. 3 totaly different companys are using Mobil 1,they must know something! Why dosen't Mobil just thicken up the oil a little?