UltraCool are synthetic refrigeration oils from Fuchs, designed specifically for ammonia (NH₃) systems.
Specifically, Reniso UltraCool 68 is a grade that is synthetic hydrocarbon‐based (not mineral), and built to provide better lifetime, thermal stability, low oil carry-over, and good low-temperature flow.
Longer life than mineral refrigeration oils in ammonia service. Less breakdown, less sludge or varnish.
Lower oil carry‐over (i.e. less oil being entrained/lost) which helps efficiency and reduces operating costs.
Better low-temperature performance allowing usage in colder evaporator environments.
Although UltraCool 68 is non-miscible with NH₃ (KAA type), switching oils always needs care to flush old oil, ensure compatibility of seals, and ensure that existing components are clean.
Cost is usually higher for synthetic hydrocarbon oils vs mineral oils; but the trade-off is longer life and less maintenance.
Need to follow correct maintenance, monitor oil carry-over, and verify that system operating conditions (temperature, compressor discharge, etc.) match the capabilities of the lubricant.
