In the wife's Elantra for 5w-20 it was Magnatec, 10 decibels quieter than PP on my cheap meter, and for 5w30 it's Quaker State Full Synthetic.
My older 98 Tahoe was by far the smoothest/quietist on RGT 5w30.
The X5 had no change between TPT 5w30 and Quaker State Full Synthetic 5w-40.
Mustang GT doesn't seem to care.