so my friend has an 04 grand prix gt with 3.8 series 3. i have been getting him mobile 1 extended performance for his oil changes. he has about 60k on his car and is burning oil. probably a quart every 5 thousand. he went to the dealer to see what was up, and they told him he cant put synthetic oil in his car. They said, use a synthetic blend. i can get him mobil clean which is a blend. But this kind of seems like bs. why would a car burn synthetic oil faster than any other oil?