I usually use sopus or Castrol products but today I picked up the mobil 1 5w30. Walmart didn't have Quaker State Ultimate Durability in the 5w30 flavor. It was 22 dollars for a 5qt jug so it was only one dollar more then Quaker State Ultimate Durability so why not. Now ive heard that using m1 can show more iron in the used oil analysis but im not sure about that. Anyone hear use m1.