Castrol synthetic or Valvoline?

After fifty years of trying to figure out what oil is best, I came up with what I think is a good choice. Look to who has the most to use by thier choice of oils. Ford Motors can't afford to put anything but a very good oil in thier trucks. Thier reputation is on the line, and Billions of $$ is at stake! Make mine. Motorcraft blend, in the right wieght for my bearing clearances.

I use similar logic for my replacement parts and engine oil.

Make mine Mobil1, aka factory fill on Viper and a few others.

That said, unless you're choosing Scamsoil or Lucas, I think all major oil brands are comparable, IF a person selects the correct oil for the application.