Talked to an old timer who made me rethink compressor oil choices

Met this guy at a parts counter last Tuesday who must have been repairing fridges since the 70s. He told me he never uses synthetic oil in older compressors because it can strip out the mineral oil residue and cause seal leaks. Got home and checked three units I had on my truck, turns out I'd been mixing oils on two of them for years without realizing it. Has anyone else heard this or am I just getting paranoid about my compressor swaps?

2 comments

2 Comments

eric_ramirez6714d ago

Heard a similar thing from an HVAC guy I know who's been doing this since the 80s. Said the seal swell comes from mineral oil over years, and synthetic can wash that out fast on old rubber. Worth checking your supplier's spec sheet next time you stock up.

wade55820h ago

Whoa hold on there, that's mostly right but the seal swell thing ain't exactly how it goes. Mineral oil based refrigerants can cause rubber to swell SLOW over time sure, but synthetic oils don't just "wash that out" like soap. They actually shrink the rubber back because the molecules are different and they pull the old absorbed oil OUT of the seal. That shrinkage is what causes the leaks, not some cleaning action. Seen it happen more times than I can count on compressors that had R22 swapped to a 407C or something without swapping the elastomers first. Your HVAC buddy might be confusing the end result with the actual chemical process.