There is a seal that goes bad and then oil bypasses the tensioner. Using thicker oil is a temp fix.
Be very careful with this. The seal mentioned is the gasket that seals the hydraulic tensioner to the block. This seal being bad can allow the engine to skip time, one chain link at a time. After about 60* (yes, it will run that far out of time, the phasers have a range of 50* in either direction) things get broken. Each time a chain link is off one tooth that is 10*.
Thats funny. It was running perfect before they changed the oil....hmmm
Try unplugging the VCT solenoids before starting the engine. That locks the phasers in a set position at 0* advance, and if the VCT system is causing the issues they will stop.
I'd also drop the spare tire down and inspect the FPDM bolted to the spare's cross member. They are known to rot out and can cause all sorts of issues as they begin to fail, and don't always set codes. Just find it, unbolt it, and look for a giant hole on the side that was against the frame.
If you find that spend the extra money on the Ford service kit. The failures are caused by stuff getting stuck in between the frame and the module because they sit too close together. The after market kits don't fix this issue, but a Ford service part will come with stand-off bolts that move the module about an inch out from the frame.