It only pools overnight. I can let it sit after running at temp for 4 or 5 hours and when it re starts there’s no smoke or misfire. I also find it strange it’s only on cyl 8 if it’s a pcv issue
I have a hard time seeing oil from 'below' the rings 'pooling' in the cylinder. For an amount great enough to pool getting past the rings I would expect to see that same amount contributing to other noticeable symptoms, low compression, blow by, etc. You could try investigating for a stuck, gummed or carboned up ring, maybe an oil with different detergent strategy. Some other shade tree solutions like adding a detergent (or mystery oil) to the chamber and letting it sit, I've also heard of a heavy use of 'engine braking' to load the rings differently.
I would first be looking at oil entering from 'above' via a head issue, or intake/PCV issue. I suspect that the oil is entering cylinder 8 combustion chamber at all times but is getting burned off during each combustion event preventing a 'pool' from forming and lessening visible oil burning smoke. This leads back to valve stems or PCV system as the only route for oil to enter the chamber from. I would expect a PCV issue to not be isolated to cylinder 8 though.
Other considerations, how long does it take the pool to form? Could you look for the oil trail via the borescope? (Run the truck, shut the engine off, as quickly as practical, pull the plug and insert the scope and record to see how long and hopefully where from.)
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