I always oil the threads and back of the flare, never the faces. I use WD-40 in a pen type applicator (stores easily in my bag) since the amount of oil is minimal and not in the refrigeration system I don't worry about contamination. A good flaring tool (YJ 60278) and oil and my flares don't leak (except for the one I made yesterday, but it looked perfect).
I can't see how oiling the face helps since it is ultimately about compression.
I was reading the manufacturers instructions the other day for a mini-split and they are now suggesting that you add oil to both the inside and outside of the flare. I had the same question as you, so I contacted Daikin and the rep told me that we should be using PVE oil instead of POE. It seems that the majority of the mini-split manufacturers are using PVE oil in their systems instead of POE.
Well, none of my distributors carry PVE oil, but Nu-Calgon sells it and most distributors can get it for you if requested.
You want to minimize "grip" as much as you can, same reason you oil the back of the flare. If during the tightening the mating surface wants to slide it's easier with oil. Remember, every flare is just a little different from the tool so as you tighten it down the shape may adjust a little, oil keeps the mating surface from gripping in such a scenario which leads to better seal. It's more of an extra than a necessity though in my opinion.
I've seen gas companies oil the mating surface of black iron unions for the same reason.
When I went to a Mitsubishi class several years ago, the insturctor recommended using
refrigeration oil on the flare to make sure the microscopic pores were full of something.
Nylog here also. I apply it to all my service valve caps when installing too. I got both the red and blue. It's funny how they recommend you uses the blue for poe and red for mineral but then they say you can use each for both...
Nylogs not available here, but have been using poe in a little oiler for years.
On one of the milk cooler manufacturers equipment i look after they use what looks like silicone grease on the back of the flare, never had one of their factory one leak, with that in mind been trying out aluminum anti seize grease on the back of flares after getting a tube of Loctite stuff at a car show, seems to work well and stops the pipe turning with the nut.
I carry a little eye-dropper full of mineral oil with me everywhere. I oil everything with it, including flare nuts. Oil helps when you are actually making the flare also. The amount of oil we are talking about here is so minute that even if it were to get into a system with POE, it wouldn't make a bit of difference. For everything outside of a refrigeration circuit, WD-40 and dry graphite powder are my weapons of choice. On my PMs, I spray down hinges, door latches, linkages, ball joints, etc. WD-40 also works ok for keeping certain things from weathering and rusting, but I prefer to paint items like that with an enamel like Glyptal. Sorry to get so off track there... lol
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Originally Posted by junkhound
