That engine was designed for 5W30. Ford now claims that 5W20 is OK or even preferred. Your engine will last longer and perform better if you do not use heavy oil in it.
I have seen other engines in the Ford modular family blow off oil filters when heavier oil was used. Several 91 to 93 Crown Victorias and Town Cars as well as 96 to 99 Taurus with the 3.0 Duratec.
Heavier oil has absolutely no benefit on this engine and has some dramatic drawbacks. Use 5W30 and the engine will behave better and last longer.
