Every app. is different. There is no one answer. A all-out race car, I would use a thinner oil, as you say, but I would also use a High volume oil pump, which would also mean a deeper pan.
Thinner oil needs neither a deep pan or an HV pump.
I’m going to run 0w20 on the street. I may end up with a 5w30 if the mains are a touch on the loose side but I’m banking on that 0w20.
One thing I think people miss is what the gauge says isn’t even close to the hydrodynamic wedge that’s formed in the bearing clearance.
As the clearance is opened up that greater space even with a 20w50 won’t have the same wedge developed. So you have less load carrying ability with the wider clearance.
When I was running aluminum rods the big deal was to send them out with at least .0035 clearance. That’s HUGE but at the time that’s what everyone said.
And the rod bearings always looked like roasted dog ****.
So I started closing up the clearance and the bearings looked better every time.
I forget where I ended up for clearance but it was probably a bit under .0025 or so.
It was on alcohol so I had to run a 40 grade oil to keep the rings sealed.
Which is one other reason I won’t do alcohol fuel again.
