Originally Posted by racin4ds
Cute girl, I'd have used the CTS-V in your sig instead of that land yacht hunk of GM junk! lol.
Sea foam did what is was supposed to, darker oil meant it was cleaning and doing its job. However, I never use a thin grade oil when I plan to add a solvent based cleaner like Seafoam... you should go with a 15W40.
Out of the whole list she only likes the Volvo and the Yukon.
Originally Posted by RDY4WAR
I have a 2002 Tahoe 5.3L with 237k miles. It's had piston slap since day one, though it only did it on cold starts. What worked for me was switching to an oil with high amounts of moly, especially tri-nuclear moly. I ran Amsoil Signature Series 10w-30 for a while, which has around 240 ppm, and it quieted down a good bit. I recently switched to Driven LS30 5w-30, a PAO/ester oil with around 400 ppm of tri-nuclear moly, and the piston slap is gone entirely. Even with it being 30*F out this morning with frost on the windshield, it still fired right up smooth and quiet.
Keep in mind that just because the oil turns darker doesn't mean it's cleaning. Oil turns black from oxidation. Seafoam is highly susceptible to oxidation. If you added seafoam to engine oil in a container and let it sit on a table for a few weeks, it would turn dark as well. The naphta and mineral spirits in Seafoam will attack the base oil (particularly nitrogen sites), turning the base oil black. It gives the illusion that it's working when in reality it's just smoke and mirrors. It affects the base oil in the same way as fuel dilution.
Unrelated to Seafoam, some ashless dispersants turn dark due to UV exposure (from combustion events) making the oil appear oxidized when it really isn't.
That is some GOOD information RDY4WAR. Can you ballpark how many miles you ran the Joe Gibbs oil before it stopped slapping on cold start?