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Gauge pressure isn't what the bearings get, it's only the force with which the pump refreshes the supply to the journal.
The actual local pressure is much higher, and also varies with certain other factors:
1. engine speed
2. journal diameter (actually, circumference)
3. bearing width to the closest leak

1. means local pressure goes up with RPM even if the gauge doesn't move.

2. the relative speeds of the journal and bearing surface in feet/second are what develops the oil wedge, and larger journals have higher local pressure at the same RPM. For a main bearing, it's obvious (3.000" main @ 7,000 RPM = 1,100 f/s, but a rod bearing oscillates while its journal spins so the relative speed changes quite a bit.
This is one reason why low speed truck engines have big journals: good pressure at the bearings at low RPM with low pump pressure.
This is also why it's dangerous to lug small journal motors at low RPM regardless of pump pressure.

3. for a continuous bearing surface this is obvious; however, a groove reduces the pressure to less than 50% vs. an undivided surface.
Math for the closest leak:
width 1.000"
closest leak: 50% = .500"
groove .060"
each half .470"
closest leak: 50% = .235"

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