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?

I really think it doesn't matter, as long as whatever you use doesn't dissolve the O-ring.
I wouldn't think there would be enough of whatever you use to contaminate anything.

My AC shop told me to lube the O rings with the same oil you put into the compressor.

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85 SE Daily driver with a 3.4 DOHC OBD II
88 Formula/GT 4.9 Allante Intake (My Baby)
www.fieroking.com

quote Originally posted by Fieroking: My AC shop told me to lube the O rings with the same oil you put into the compressor.

That's what me do.

Kevin

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?