The Motorcraft 5w20 is a great oil, and my 95 Tbird with the 4.6 ran fine with it. If you're really uncomfortable with a 20 weight I'm sure any 5w30 would be fine, though. As for synthetics I think Mobil 1 5w30 is good match for the 4.6
If you're going to stick with 3,000 mile OCI's then the Motorcraft 5W-30 is fine. My wife's 2002 Explorer requires 5W-30 and she used Motorcraft 5W-30 for the first 30,000 miles with 5,000 mi OCI. I did an UOA at 25,000 miles and it was REALLY good for a dino oil. However, your engine has the option of using 5W-20. Maybe you should consider using Motorcraft 5W-20. It is a greater quality oil for only about $0.40 more per quart than the Motorcraft 5W-30 at Walmart, a bargain. My dealer charges the same $22 for an oil change whether I use Motorcraft 5W-20 or 5W-30. It's a no brainer for me with MY 2002 4.6L F-150 to use the Motorcraft 5W-20. I did a UOA and it was really good. The weather in NJ is not too different from Kentucky so I would think that the Motorcraft 5W-20 would work for you just fine. The wear for Ford Modular engines using Motorcraft 5W-20 is impressive, as well as using Pennzoil and other quality 5W-20's.
The book says to use 5w20 synthetic but I bought the truck used and it had a jiffy lube sticker on the windshield so my guess is the previous owner probally didn't use the motorcraft 5w20. Ive been using motorcraft 5w30 for around 30k miles now but i was wondering if its too thin for the summers here in KY around 85-100. My truck is also getting close to the 100k mark and was wondering about these high milege oils are they for real or a marketing host. Also if I should switch to synthetic is there anything I have to do changing from just regular oil. And if I was to run thinner oil in the winter and thiccker in the summer does that cause problems. I'd appreciate your help because what oil is best is something I know nothing about.
I'm in south texas, 100 is a cool day around here. I've been running Motorcraft 5w20 in my wifes 98 expedition (5.4 engine). Her truck has 92,000 miles on it. It loves that oil. If you are going to change it up to 5000 miles you can't go wrong with the 5w20 all year round. For the price its one BAD Azz oil. Just my opinion. You can also stick with what you are using, it will work too. changing over to syn: If you want to you can always do a flush on the engine, but if its been taken care of you don't really need to. Generally just put it in and it works.