Ahhhhhhh who am I kidding, I have an opinion on everything! Should have been a circus side show
Why the heck did you build it loose? I run 5-30 mobil 1. Water basically. 80 PSI when cold. 25 at HOT idle, 30 normally and it goes up about 10 psi per 1000.
If I was going to build loose, I would put in a high volume pump.
Of course, you could try gear
oil. There is a some good 80W-140 weights out there.
Rick