What is interesting is that carbon cleaner has been noted to help with piston slap. If that is true, then the piston rings on one or more pistons must be stuck in the ring land, not allowing the rings to properly support the piston in a cold running state. Most pistons are cam ground, meaning they are egg shaped when cold, and when heated swell to a round shape. The carbon theory may hold creditability. This might explain why owners of piston slapping GM products have higher oil consumption. The stuck rings are allowing excess oil to enter the cylinder chamber. Carbon is very hard and difficult to remove. Diamonds are formed from carbon. The cleaner must be one of the harshest chemicals in the automotive world. As the carbon cleaner activates, bits of carbon may be trapped between the top ring and the scraper ring or elsewhere, scoring the cylinder wall. Thus, one has traded one problem for another more serious problem. Therefore, I would not recommend the carbon cleaner. My solution is to use a 5W 20W motor oil and drive it hard once it is fully warm. The high RPM and Piston loading will eventually free up the rings, to some extent. Change the oil every 1200 miles for the first three oil changes. Viscosity Improvers in modern motor oils begin to lose their effectiveness after 1200 miles. The GM engine needs the full 20W characteristic in operation to provide proper protection. A long drive will allow the detergents in the oil a chance to dissolve some of the carbon and or sludge, which are sticking the piston rings. Piston slap is not all bad. Frictional losses are greatly reduced because the engine has reduced piston skirt drag. I would prefer that GM built my Suburban with out the piston slap, but this particular issue is not as bad as it seems. The aforementioned process has worked well for me. Sometimes I hear a little slap when she is cold, it could be a lifter, but she runs great and is silent when warm. I run a 5W 30W Castrol and change it every three months with a GM filter. 106K and pulls like a mule to the 100 MPH cutoff. 2001 K1500 5.3 original mint condition, 106 K, silver with silver cloth interior, console with key, fog lights, 265 Michelins.