Yes this has been beaten to death, but I run Rotella T6 5w-40 in my 360 magnum. I have several reasons I run it, but the big ones are:
- It's a heavy duty full synthetic that still contains a fair amount of zinc (1200 ppm tested), and is intended for applications that would cook a normal oil. That may be a little overkill, bit I don't see it as a bad thing.
- I like the viscosity range. It gives me good hot oil pressure, and being a 5w when cold it may get to critical parts faster at start-up. I don't know if that really makes a difference, but I like to think it does.
- And last but not least, it's cheap as far as synthetics go. I buy it at Walmart for $21.36/gal. The only downside is you need to buy 2 gallons to do an oil change, but I use it in every vehicle I own so I usually have several gallons on hand.
Also, to give you a reference, hot idle for my engine is 20-25 psi (~ 800 rpm), and hwy cruise (~2250 and up) is 60 psi. This is with a standard volume pump. I also had low pressures when running 10w-30, but 30 psi does seem low to me. What rpm is that?