Had the oil changed on the wife's van. Since it's too stinking cold & snowy to do myself, had to settle for the "special" at the local autoshop. In went Dino 5w30, out went 5w30 M1 full synthetic (6k miles on it). When using the m1, every morning you could hear the clanking of the Rocker arms for 10 seconds or so. Using Dino, no noise. My theory? The M1 flows so well, it's all back in the oil pan while the Dino leaves some in the upper part of the engine. I use M1 80% of the time and think it does well in all my vehicles. Just an observation.