Blue smoke on extended idle. 2006 4.8is.

[JCL]

Originally Posted by danielsan

I was thinking when i had my old LS1 engine rebuilt the shop that did it advised not to run a synthetic oil for the first 5,000kms to allow all the rings and seals to bed in properly.

I'm wondering if running a synthetic oil during the break in period of these engines is what's causing alot of these seal issues as they age?

You can use a modern synthetic from km zero. It isn't the oil that changed, but rather modern engine manufacturing processes. I recall the break in instructions from 30 years ago suggesting non synthetic oil. That has nothing to do with valve guides, but rather cylinder bore surface finish.