Motorcraft synthetic blend is a good product, but I would suggest you make your own blend. Since you are already using Mobil 5000, just add-in 1 or 2 quarts of Mobil 1 and you will be way ahead in terms of quality (and probably cost).
If you have a Costco membership, they have coupon coming up May 11-31 that gives $10 off a 6-pack of Mobil 1 motor oil (5W-30 and 10W-30 only). Even if you use 5W-20 for your Mobil 5000, just add-in some Mobil 1 5W-30.