C15 Low Oil Pressure

So, I've had low oil pressure on this engine since I bought it. It is a 2006 MXS prefix ACERT. It has a fresh rebuild on it and before I bought it it all seemed normal to me being as I was used to the ISX that I'd been driving for the previous eight years that run lower oil pressure than the Cats. I learned after I bought it that what I was seeing was below what it should have been. My fault and a definite learning moment. So what I see is at hot idle it's only around 20 psi, maybe a bit higher. At 1500 rpms it only gets to around 55 psi, never over 60 unless it is cold. I took it to my mechanic who is really experienced with the Cat engines and he did a bunch of diagnostics before finally suggesting that it may need a new oil pump. I've attached a picture of the writeup he did so you all can see what all has been looked at. After he replaced it it basically made no difference. I gained maybe 5 psi at first but it has since dropped and held right where it was before. He was confident that as long as it doesn't drop further that I will be ok as it is technically within Cats specifications. I am very uncomfortable with it though. Maybe I don't need to be but I wanted to put it to the collective here and hopefully get some thoughts. Thanks for any input!

 

Yes they did confirm it with a mechanical gauge.

 

I don’t know what was in it when I bought it but when they dropped the pan for the pump I had them put in T6 5w-40. I’ll try something different next time. I’ve seen several posts of people saying that Delo helps with their blow by so it’s worth a shot.

 

It is only thinner when cold. Same viscosity when hot.