[brownie21]

I have added K-seal in mine recently as I had a constant small coolant loss. K-seal can be left in the system permanently according to the manufacturer and I have only read good reviews about the product. Those who say 'don't do it it will kill the engine' need to come up with some concrete facts supporting this claim. It doesn't go 'sludgy' and doesn't blocks the waterways. You end up with very minute particles in the water which will eventually pack together at any small leak points (including head gaskets) to seal them up which can take a few days.
Saying this I have since found out that I have a suspect water pump which is causing the loss which I am having replaced shortly. Still leaving this stuff in though and I have no worries about using it. Never heard of the other one though.

Rgds

Wayne