I've heard that it's a BAD idea to use Ester or PAG oil to lubricate o-rings during installation, and that mineral oil is the right stuff.
My question is - why can't a generic light oil (motor oil, ATF) or another petroleum type product (vaseline) be used? Isn't the purpose of the oil just to allow the surfaces to slide, so the o-ring isn't torn during installation?
They make a special lube called Nylog. I've used it on all my AC seals on every vehicle I've worked on. I pull vac on the systems then let them sit overnight and haven't had one leak yet. I would not use the the compressor oil. I don't know if the oil is good or bad, but I know this stuff works.
I think the theory is something like this: You don't want to use a hydroscopic oil (like PAG or Ester oil) to lubricate o-rings, because these oils will attract moisture and cause corrosion at the fittings.
I've heard of Nylog but don't have any handy. I do, however, have a ton of other lubricants, which is why I was wondering how important the oil type is. Will regular motor oil react poorly with refrigerant?