Here is my take on this oil issue...
For many years I have used Castrol oil, usually a 20w-50 in most of my cars, to my memory, after changing the oil and filter, most of these cars seemed to run better, less oil usage, better fuel economy, etc.
But we are now faced with many different "oil formulations", how are we supposed to make an informed decision?
I tr to keep it simple, if the oil you have used in the past, on any other cars, seemes to work for you, then just upgrade that oil to what you need in your Vette.
You will find hundreds of compairsons of any oils lubricating qualities, but what you need to look for is the oils ability to remain viscous at low and high temps, in relation to the environment around them.
You would not want a 20w-50 oil in canada, it would become heavy syrup in winter, as such, the same oil in Florida may remain to thick to allow easy start-up, which creates an unnecessary load on the internal parts of the engine.
As I have stated before, I have always been a 20w-50 guy, now I am changing my thoughts on this.
I think that a lighter oil, say, 5w or 10w, may actually be more beneficial in the long run. However, if you have an engine with over 50k miles, you may want to run a heavier oil or an addative to a lighter oil.
I have been using 20w-50, on my next change I will try a synthethic 10w-40 and keep you up on this.
We shall see,
Joe B.