I've had a small leak on my car which I think is the intake manifold or coolant elbow - I always see these engine oil additives like GoldEagle's No Leak, Bar's Stop Leak, AutoRX, Etc... do these things really work? They explain that they clean and rejuvinate the seals by swelling the gaskets. These products are also backed by a money-back guarantee.
Anyone have any experience with any of these for minor oil leaks? Success or failure?