Ok, tbh I don't know for sure, but let's go ove. This

you put that blue devil ahit in ur engine, that has a extremely high viscosity and is designed to swell all seals it comes into contact with. There are 40+ little seals gaskets, and prongs in that engine. When some of them expand it can cause learence issues, although minor ones, that could cause clicking till they get re-worked it

the higher viscosity can also cause problems, untill it gets fully mixed in and burned fluid.

Older engines, especially fords, usually develop lifter ticking, my dads 01 4.0 explored ticked pretty good at 40k miles. They are roller lifters so they have moving parts that can ware ant tear.


There are so many possibilities it's not even funny, like snaw said, could of even been a price of dirt