I have a good customer who is in the food industry, and has flash freezers that go to -40 deg. F.
They use two different types, both food grade (H-1). For the flash freezers, they use CHevron Tegra synthetic compressor oil, ISO 68. The main problem they have is water ingress, which destroys the gearbox before anything else has a chance to. Seems the sanitation department like to have the sprays right on the shaft of the gearbox underneath the drive cogs.
For the coolers, which are at 0 deg. F, they use the manufacturers product, which is a Frigo oil from Frigoscandia (JBT). FRIGO 410, LOW TEMP, part no. 350945C.
Dave