I have a 2003 f150 with a triton 5.4 in it a few days ago I noticed the engine would make a knocking sound so I checked the oil level and it was fine then I did a little search and someone said they put oil treatment in their truck and it stopped so I gave it a try hoping for the best and so far no change. The engine only knocks when cold when the engine warms up it sounds normal one guy told me it might be a piston slap and it could be fixed by rebuilding it.
Just wondering what others opinions are if it is a piston slap and if rebuilding it would fix it or any way to fix it.

Thank you

 

Piston slap sounds like a muffled clatter. Cam followers make a tapping sound and timing chains rattle. I'm just throwing that out to maybe help you determine the source. Rotating assembly noises break down into rod knock which is a fairly sharp crack, and main bearing which is a deeper thump.
If there is any serious internal issues beyond valve train/timing chain, I'd consider a reman engine from a reputable source. Jasper has a pretty good reputation.

 

If the noise goes away when the engine warms up it's not likely to be rod knock. Could definitely be piston slap. If it's piston slap it could continue in its current form for an indefinite period or could eventually get worse over time.