I have been using RedLine 10W-30
synthetic in the winter when it is cold and Amalie 20W-50
synthetic Pro Grade in the summer when engine temps are higher. This is the regime that has proven to work well in my 428FE. Amalie is rather hard to find but if you call them up you can usually find a distributor in your area. Both are excellent
synthetic oils however neither are they inexpensive.
The engine was broken in with non-synthetic
oil for the first 5000 miles.