I had a startup rattle on 5W20 Mobil Super, it was 1/2 a quart low so i added 1/2 a quart of the Supertech HD30 (SN) and the car idles smoother, and has no startup rattle, so i guess i need a thicker oil for my next oil change, i was always going to switch back to 5W30, so does this confirm that need, or is mobil super 5W20 just a thin 5W20?