I'm not one to usually hype a product, especially not motor oils and stuff like that, but my work car(01 saturn 4 banger) has ALWAYS had an engine tap on a cold start for about the first second. Other saturns do it too so I just figured maybe they have issues until the oil gets circulated. Well, I swapped from dino to valvoline synthetic and it still did it. My last oil change was with Mobil1 and it still did it. It came due last week and I just paid for my Amsoil membership so I ordered some of their regular 5w-30. Every cold crank since then has not made one sound. So for the first 40K miles it was an everytime thing, then one oil change to Amsoil and the first cold start and every one after that, no noise. you do the math on that.