Maybe all the PP fans are on to something. When started cold, the "Gray Goat" would make a piston slap type of noise for the first minute or so than it would go away. I am not sure if it did this with the oil that was drained with the first change, but it sure did it with the 5w30 Motorcraft semi syn. I started it up after work yesterday, cold, and did not hear it. At that time it was just a mental note I made to myself. I paid attention the next couple time it was started cold, and the sound is gone. Hmmmm, could an oil do that? The one drained and the PP put in was both 5w30. Same filter too.