lubricant selection for a custom expander

[cdatgnp]

Hello all,
I have a machine that needs a new lubricant, but I don’t know what’s important to look at when comparing lubes.
The quick & dirty is:
- it’s a 180 kW screw expander (like a screw compressor in reverse, but the screw faces run ‘dry’ – no lube)
- oil is circulated to roller bearings, gears and mechanical seals, for lube and cooling
- a design change will bring butane vapor into the gear sump, so we think a hydrocarbon-immiscible lube is necessary to avoid condensed butane from cutting the lube and reducing its viscosity
- the lube will be maintained at about 82°C (180°F) to avoid butane condensation in the sump
- due to logistics, we want comfort that our machine will be able to perform for at least a couple months to prove the technology
My boss is having me look at what ASTM tests are important for comparing lubes to each other.
My questions for those in the know:
1. How can we better approach this selection?
2. Are there ASTM tests that can allow us to compare lubes for efficacy?
3. Do lube vendors typically perform many of these tests? It seems like D92, D97, D445, and D4052 are the staples.
4. What do you think of using a conventional or conventional 1X or 2X end-capped polyalkylene-glycol lube for this application?
I am grateful for any advice.
-Chris

[RANGER1]

Chris,
Have you approached compressor supplier for recommended lube oil?

[cdatgnp]

Ranger, it's our company's design under development by our contracted manufacturer. The manufacturer specified the original oil, but the pending design change will make it unsuitable. I guess what this boils down to is I am asking what's important for selecting a lubricating oil? Are there ASTM standards we can use for comparison?

[RANGER1]

Not my area of expertise but CPI are helpful in USA/Canada.
Oil compatibility with compressor seals etc very important.
Most screw use 68 viscosity oil.