Its the quaker state oil. Motorcraft, exxon, and mobil 1 all caused weird noises in my panther fleet. Since moving to only QS oils (honestly becuase of price not brand loyalty) my startup sounds are gone. Walmart ran an insane sale in the end of 2019 early 2020 and I bought up like 50 containers of QS 5w-20.
Now, there is a hidden secret going on with these engines that the jury is still out on......The 2004 and newer models used a plastic body timing chain tensioner block with a molded oring to seal the oil pressure. The wall holding this oring is thin and will warp with age and allow some oil pressure to leak out. The good news is this loss of tension is on the non load side of the timing chain so performace should not be negativly impacted. But they will rattle at start up.
Prior to 2004 they primarly used a metal cast tensioner block with a ratchet that would hold pressure on the chain. these were better in my opinion but some will stick and rub the tensioner thru to bare metal.
