Pennzoil Platinum - my only choice.
Over the years I have used Redline, Mobil 1, Royal Purple, Amsoil and Pennzoil Platinum. Today I own two vehicles, both daily drivers. I use PP 5w30 in the wife's van and Amsoil 5w30 in the Tahoe. The van gets a 5,000 OCI (currently has 25,000 on the clock) and I am trying to run the truck to 20,000 on this latest round of Amsoil (150,000 on the clock). I doubt I will make it...I think 20K is a bit much for the same oil. I'll probably pull the plug around 15K.
Once I change out the Amsoil in my Tahoe I will go to PP. I can get it at Wal-Mart, it is well priced and it is a good oil. I will stick with the 5K OCI on the van and 10K OCI on the truck. The van has only ever had PP...the truck has had a variety. If I had unlimited money then I would probably buy Redline oil since I think - my opinion only here - that it is a fantastic oil. I believe that PP is the best off the shelf, available at Wally world oil out there.
I guess the best syn oil or the ultimate syn oil for you to use is the one you deem the best for your application.