That 3.9L V6 engine (I have one) is a known sludger because of intake manifold gasket seal issues. I ran only QSUD synthetic and just used the manufacturer's OCI, and when I had my heads done at 115K miles (non-lube issue) I took a look, my galley was clean as can be.
He said it's been running 10w-30 lately, I bet it's conventional, nothing wrong with that but it's unlikely to get a leg up on the sludging already there.