[Pvt Parts]

Originally Posted by Alan Roehrich

Bub,
I understand that. What I'm saying is, the best way to get some idea of what gain can be had, without taking everything apart and spending a fair amount of time, is to try a really light weight oil.

Sure, the difference in friction between the oils will have an effect, but not as much of an effect as the reduction in HP spent turning the pump.

Once he sees what using the lighter oil will do, then he can look at what he needs to do to run lower oil pressure without risking damage. He'll probably gain even more power, and be pleasantly surprised.

Triple XXX Correcto !!!! Doing that reduces the HP necessary to turn the pump and the improvement in lubrication reduces the parasitic drag. And your forgot to mention that with improved lubrication, you can probably get by with less oil in the pan thereby reducing windage.
Unless he's saying he has those pressures with 0 wt oil now. In that case, take it apart.