Hi Jamie,
Here is my take on this, so JMHO. A long time standard for oil pressure is 10 psi for every 1000 rpm. So, 20psi @ 2000rpm, 30psi @ 3000rpm...etc...etc. That being said, pressure is important, but more important than that is flow and the amount of oil getting to the bearings. The more oil the better the lubrication taking place. The more oil going to the bearings, the more heat is displaced to the pan for cooling. The thicker the oil is, may bring up pressure, but also reduces the amount of flow to the bearings.

For more information try reading this thread that I commented to January of 2021. Lots of info and comments from others here. JMHO

http://gmc.mybirdfeeder.net/GMCforum/index.php?t=msg&goto=362020&rid=19&srch=engine+oils#msg_362020

If you read that blog you would find that the methodology used is very basically to rub two pieces of metal together while pouring oils tested between them and applying pressure until the metal breaks through the oil film, scoring the metal. The Rotella 15w40 is rated at #222 (at 72,022 psi) of the 279 oils tested. Maybe take a look at #71. 10W40 Valvoline MaxLife High Mileage synthetic blend (red bottle) = 103,840 psi. With that you would get the 40w for hot running and a 10w for better oiling at cold starts. Also the extra advantage of seal swelling additives to reduce oil leakage. Personally I would go with #16. 0W40 Mobil 1 “FS” European Car Formula, synthetic = 127,221 psi. You would have much better wear resistance @ 127,221psi with the 40w you need for hot running and 0w for good flow to bearings on cold starting. I am now running #1 on the list 5W30 Quaker State “Full Synthetic” in the green bottle, @152,674 psi. I use to run the Mobil one and recently changed to QS 5w30. Oil pressure drop when going from the 0w40 mobil one, to 5w30 QS was 2-3psi at a hot run, and raise of 5psi at hot idle. Oil pressure now is 42-45psi hot highway speeds and 25-35psi at a hot idle. The QS 5w30 can be had for about $23 per 5qt pail at Walmart, a pretty reasonable price. You can also raise the oil pressure by dropping the pan and installing a high capacity oil pump.....a lot of work with only maybe getting higher oil pressure you are looking for.

Just my relatively informed, off the cuff, back yard mechanic, gut level, eyeball it up and guestimate, (based on some actual research) opinion...that's all...

One more thing to consider, how multi vis oil is made with dino vs syn.
Dino 10W-40 for example is 10 weight oil. They add long chain viscosity modifiers to get the 10 to behave like 40 when hot. The oil molecules are still really 10 weight. With use the viscosity modifier package is exhausted along with other additive chemicals.
By design, true synthetic oil behaves more like multivis. On both ends. It flows better cold so it can be thicker at room temp and still get the 10W rating. It also tends to thin less at high temps. Because of this, less or in some cases no viscosity modifiers are needed to get the multivis rating with syn. This also increases oil life as less or no viscosity modifiers to break down with use. They tend to be broken down during extreme conditions (motorhome duty).
In my opinion, based on cost to R and R a TZE engine, shorter oil change intervals are money well spent. Several factors go into oil change intervals, but one cannot be denied. Fuel rate and associated combustion byproducts. In rough terms our fuel rate is about double the Toronado (9 vs 17-18). That makes me think 1/2ing the oil interval is wise. Double fuel rate makes double the combustion water, though the high loads help to remove that water, the acids build up. Then we park it for months on end. A bad formula.
I’d try a true syn as Larry (and Dick Patterson) recommends. Some oils are syn rated as they perform like syn but are not syn. Also Dick recommends not exceeding 40 hot rating.

Jamie,

I guess you don't know that the pressure of lube oil delivery is substantially unimportant. If you had more experience with engine development, you would know that on the list of things lube oil does in an engine, hydraulic pressure lubrication (that were the lube oil pressure supports the bearing journal) is way down the list. Were this not true, plain bearing engines could not survive with a splash lube system.

This has been stated before, but here is the list again:
1- Cooling Very - Important to cool the underside of pistons
2- Damping - To stop parts from ratting and damaging each other
3- Flushing - Remove debris created by wear and combustion
4- Working Fluid - as in hydraulic lash and chain adjusters
5- Prevent surface contact - any place metal parts meet like cam faces
6- hydraulic wedge lubrication - how it works in a splash or 2 stroke engine
7- Gap filling - very much like 2 and 5 but specific to irregular parts
8- Pressure support of journal bearings - this is crank and rod bearings
9- It seems I forgot one as I used to know nine, but the last was what I have as eight.

Even with the low lube oil pressures at idle, the hydraulic wedge is still what actually makes the bearings work. This is also a great way to understand why lugging and engine is so very bad for the bearings.

You can worry about this if you choose, but don't really start to sweat until you can hear the dry lash adjusters (lifters) rattle.

Matt - The refugee from dyno land

I would keep the 180 thermostat. The 195 can make the oil a little thinner and lower the pressure a little more. I run Rotella 15W40 and a 180 thermostat.