What's the general consensus on what lubricant to use on O-rings? For example, for fuel injectors, the service manual says to use motor oil. On others, I've read that a little vaseline is used. Is there such a thing as O-ring oil? And, does the location of the O-ring dictate what is used? (you wouldn't want oil on an O-ring used for coolant). In my most recent experience, I'm replacing the O-rings on the inlet and return lines of the fuel block.

quote Originally posted by sledcaddie: And, does the location of the O-ring dictate what is used?

I think the only place where it might make a difference is at brake and/or clutch hydraulic connections. Just use brake fluid on the O-rings... and obviously use the same type of brake fluid as what 's being used in the rest of the system.

Elsewhere... motor oil, ATF, vaseline, whatever. I suppose however that using spit on O-rings is now frowned upon.

Lubing AC o-rings with the wrong lubricant can cause problems, too. Something that's compatible with all automotive, commercial and residential refrigerants is Nylog Blue. Just a tad goes a long way. It actually is a good sealant as well as lubricant. I wouldn't be afraid to use it on injector o-rings, either. It doesn't dry out and get hard, so if you ever had to pull an injector there would probably be no damage to the o-ring. It's available at most HVAC supply houses. A tiny bottle would likely never be depleted and it lasts forever.

quote Originally posted by fierofool: Lubing AC o-rings with the wrong lubricant can cause problems, too.

Good point. I never even thought of A/C O-rings, perhaps because I don't use A/C.

Engine/Trans just use same oil or whatever that goes in the parts to seal the area.
Coolant parts can use straight coolant or brake/silicone grease/oil. Like can lube T-stat cap area to prevent rust but don't use engine and many other oils/grease or will wreck the seal.

Lube Brake "O-rings" and other parts can depend where the part lives when done.
Some can lube w/ clean Brake Fluid. Many get Brake Grease.
Sliders and related rubber parts get grease.
most piston seals just get fluid.
Dirt boots/seals need nothing or tiny coat of Brake grease.
See my Cave, Brake Service and the rest of section.

AC uses same AC Oil that system uses or Nylog on most joints, O-rings, etc.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Thanks to all for your input.

The advantage of Nylog Blue on AC joints is that it doesn't harden and also acts as a seal.

quote Originally posted by fierofool: The advantage of Nylog Blue on AC joints is that it doesn't harden and also acts as a seal.

I second this, Nylog is amazing and would never go without it, especially for AC work.

quote Originally posted by fierofool: Lubing AC o-rings with the wrong lubricant can cause problems, too. Something that's compatible with all automotive, commercial and residential refrigerants is Nylog Blue. Just a tad goes a long way. It actually is a good sealant as well as lubricant. I wouldn't be afraid to use it on injector o-rings, either. It doesn't dry out and get hard, so if you ever had to pull an injector there would probably be no damage to the o-ring. It's available at most HVAC supply houses. A tiny bottle would likely never be depleted and it lasts forever.

I too have used this stuff on AC o rings. It would likely be great for injector o rings. Ordered mine online, Amazon or Ebay.