For what it's worth, I used to own an 2003 Mercury Sable with the same 3.0 liter Duratec V6 engine.. The engine, when it was first released, specced 5w30 oil, and was later back-specced to 5w20 for CAFE requirements. I used to regularly run anything from 5w20 to 5w30 to a blend that even included a little 10w40 mixed with 5w30.. and the engine never really seemed to care that much.
... I also ran numerous OCIs out to at least 7,500 miles.. and again, no obvious problems, so in my humble opinion, you could run a wide range of oils in yours.
However, the current Ford spec for that engine is Motorcraft semi-synthetic 5w20.. but I got my Sable's 3.0 Duratec out to 189,000 miles before I sold it, running all sorts of different oils.. so draw your own conclusions.
FYI - my driving was about 80-90% highway driving @ 70MPH+ so a longer OCI was easy.
... as to your current situation - If the oil has been in there a long time (6 months+), or if you do a lot of stop-and-start driving, etc.. then I would consider changing it out very soon. Otherwise, if the 4000 miles has been long-trip driving, then I personally would say you could stretch it out to 5000 before your change. What oil is in there right now?