I'd started looking this morning, then had to run...
Hi Andy,
Welcome to the Forum!
Good question. I'm not finding a specific reference for oil types/viscosity for Podmore pugmill...
...nor for "Opperman spur reduction" gearbox, which appears to have been standard for some time with Podmore pugmills.
Hypoid oil is important for ...hypoid gears!
Still have the drained oil? Might be helpful for comparison.
You might go with a semi-synthetic (cheaper than full synthetic) multi-range hypoid gear oil.
How warm/hot the gearbox gets, important, as Bill has pointed out.
If you absolutely do not find a spec, I would consider trying hypoid general purpose gear oil, likely in the 90w range and observe the heating in early operation. I would hope there are no significant swarf to speak of from machining operations and he was concerned about break in.
