Howdy
I am trying out the Amsoil 20w50. It is a newer product from them with a diesel rating.
I am trying it in my 1996 6.5 that has the typical low oil pressure syndrome and my daughters 1998 6.5 that is pretty normal. On first try I gained 5-7 PSI (factory gauge) on the 1996 and about 10 psi on the 1998.
The 1996 would normally run 20 at hot idle and MAYBE get to 30 on the road, now it is at 25-30 hot idle and 35-40 road!
I did also change the ops on the 1996 so that may have had something to with it.
Anyways just putting it out there that there is another option that might help the low psi of some engines.
Also if you are into extended drain intervals this might be a good option.
Hope this helps!