One of three articles supplying a practical guide to refrigeration. States that with the advent of HFC refrigerants came a requirement that all the mineral oil be removed and replaced with POE (polyolester) lubricant. Notes doubts about whether such replacement was always necessary. The issue has been complicated when refrigerant manufacturers and formulators recognised that blends containing a large proportion of R22 (R401A and R409A for example) exhibit sufficient miscibility in all but ultra-low temperature applications to function like the old HFC/mineral oil systems without changing lubricant. Addresses only HFC (hydrofluorocarbon) refrigerants and blends that are not miscible with mineral oil. Explores factors that favour using or retaining mineral oil when retrofitting existing systems. Also discusses potential problems arising from such use or retention. Describes in a separate section how to handle a theoretical refrigerant replacement/retrofit by discussing the alternative approaches.

Article appeared in the Practical Guide to Refrigeration, which was included with the vol. 41, no. 11, November 1999 issue.