That stuff really does work, but that's not the point. It is indiscriminate when it works. Meaning if there are any contaminants or anything else in the system that can "activate" the sealer, it can plug up your expansion valve or form a coating inside your evap, condensor, or hose passages. I've read here on the forum of instances where things were gummed up on the inside necessitating total replacement when the system was opened up for service somewhere down the line.

As for O-ring conditioner, I think the very nature of that concept is gimmicky. Think about it - do you have to condition head gaskets or brake caliper piston seals or crank main seals? No - you just replace them when they fail. If you have ever removed an O-ring from an A/C fitting you will see that the thing gets "crammed" up in there pretty well, to the point that I'm not sure how "conditioner" could help one that has decided to break down. In my experience the problem tends to be that the o-ring gets deformed and loses elasticity from being crammed in there for many years and then begins to leak. Either that or the fitting is corroded (in northern climates), in which case just replacing the $0.35 o-ring or clean/replacing/rebuild the corroded hose.

In my estimation, the correct way to remedy leaks is to replace the part or (usually) the seal or o-ring that is leaking. Stop leak is just a band aid if you don't plan on owning the car for any length of time. Just have pity for the next owner...

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