My experience is that the numbers say nothing about the quality of an oil. If you look at the datasheets you will find some 5W-50 oils which are much better and "thicker" than some outdated 10W-60 oils. You have to check the datasheets and not the numbers. And a "thicker" oil isn't autmatically much persistent than a "thinner" oil.

For daily normal / hard road use I wouldn't go higher than "..5/10W-50", never mind how much power the car has. A good 10W-60 only for race trim or if its really recommended for the engine.