Ok, because I can test this with different oils I did, here are my results which are in no way scientific or measured more accurately than the oil gauge on the dash of my work van.
2006 GMC 1-ton with the 6.2L Duramax diesel, 190k when test was started.
I get my oil changed at a quicklube.
First I used Valvoline All Fleet Diesel oil in 15w-40.
Valvoline.com > Products > Motor Oil > Diesel Motor Oil > Valvoline All-Fleet® Plus Engine Oil
Changed every 5,000 miles, when new the oil psi would be 62-64psi at cold idle, and 20psi at hot idle.
While driving oil psi while hot would be upper 40's to low 50's.
The oil psi gradually got lower as the oil got worn out, after 5,000 miles at cold idle oil psi would be upper 40's and at hot idle it would be around 10psi, a needles width over the red line on the bottom of the gauge.
While driving oil psi would be upper 30's to low 40's.

Switched to Shell Rotella 15w-40.
- Diesel Pickup
Oil psi at cold idle when oil is new was upper 40's to low 50's.
At hot idle it was upper 20's.
While driving oil psi was in the upper 40's.
After 5,000 miles cold idle is mid 40's and hot idle is mid 20's.

So while the oil psi numbers are not higher with Rotella they are more consistent over the life of the oil.

This is a delivery truck that runs for 8+ hours a day and is driven hard.
So in my non scientific real world test Rotella seems to hold up better than Valvoline.

 

Thanks for the info...I think your real world test means a lot more than the scientific crap we are fed from a lot of these companys .....

 

I think lab "tests" can be tweaked to show the results that you want.

 

you betcha ! Even an "independent" lab has to be paid by somebody