When my truck has been sittin for a complete day and the engine is nice and cold, i crank it up and someone could mistake it for a Diesel when first cranked up. Im using 5w-30 Mobil 1, it made it less noticable since i changed from Castrol GTX 5W-30.

Ive been doin some research, got some info from it.

But what exactly is Piston slap? What ill effects can come from it?

Just wondering, because a Turbo is fixin to go on (6psi).

Any links are very appreciated, i want to know whats goin on inside the engine.

If it knocks pretty bad, i let it warm up and stop knocking till i go anywhere.
Once goes away, i never hear it till it cools off for a day or two.

 

I read somewhere that it's the piston skirt hitting the sides of the piston walls, but I could be wrong. Brand new car/trucks make this noise also. Are you sure that it's the piston slap, and not a lifter or a rocker?

 

My father in laws yukon does the same thing. He talked to the guys at GM they said its normal and alot of these motors do it and theres nothing that can be done to fix it.
Make sure you don't use a 10w-30 or 40 or it will make it worse. stick with the 5w-30

 

Im thinking about replacing the Oring soon. just to be sure.
But im sure its Piston Slap. I did have a slight lifter tap, and it disappeared when i switched to Mobil 1 also.