What kind climate do you live in?
If its California, 20/50 or 30 covers most.
East coast, 10/30 or 30
I think Chrysler had it right with where the middle of the road was..30 wt.
You can technically run 5/20,30,40 etc...
Heat fades the psi as much as 15psi or so shown more at idle on the gauge. 20/50 was chosen as the general race weight because of it's good operating temp range protection aka viscosity sustainability from low to high rpms and film strength for momentary air pockets in the system, 'think pickup gets uncovered with g forces'
Me.. I run Schaefers superme 7000 20/50 para synthetic.
