Rotella 15w40
Check the current spec sheets and oil analysis (virgin and used) that people post on the web.
Many oils including the Rotella line were revised about 5 years ago.
It depends what bearing clearances the engine has and how it's going to be used.
This ^^^^^^^^
Here's what was posted in:
Oil Viscosity vs Bearing Clearance
and discussed in posts here
Valvoline VR-1 vs. Lucas Hot Rod oil
[Below is quoted from the thread linked above. I'm not a builder and in no position to say whether they are good guidelines based on my own observations and experience, but they appear to be.
For general use, its usually better to use a multi-grade.
Whatever W portion is in front will provide better lubrication when the oil is not fully warmed up than a straight grade. One they are at operating temperature, the viscosities are about the same. That said, 40 and 50 grades tend to have better high temperature, high shear performance.]
Multi-grades.
Some recommended rod bearing oil clearances for various oil viscosities:
.0015 to .0018 for 0W20 or 5W-20
.0020 to .0024 for 5W-30 or 10W30
.0025 to .0029 for 10W-40 or 15W40
.0030 to .0040 for 15W-50 or 20W-50
For main bearings:
.0015 to .0020 for 0W20 or 5W20
.0020 to .0025 for 5W-30 or 10W30
.0026 to .0030 for 10W-40 or 15W40
.0031 to .0041 for 15W-50 or 20W-50
Single Grades
Rod bearings with
.0015 to .0018 use 20
.002 to .0024 use 30
.0025 to .0029 use 40
.0030 to .004 use 50
For main bearings:
.0015 to .002 use 20
.002 to .0025 use 30
.0026 to .003 use 40
.0031 to .0041 use 50
After break-in, depending on how it was machined, probably best to use a conventional base stock for a few thousand miles.
One current option for a conventional oil with decent Zddp levels is "Ford Super Heavyduty" which meets FORD WSS-M2C171-F1
some specs here
PETROLEUM QUALITY INSTITUTE OF AMERICA TEST PROGRAM
The higher the spring pressures, the more concerned I'd be about the ZDDP.
800 ppm is pretty good.
For a cam that's somewhat radical, I personally prefer an oil more around 1200.
