First off, why do you need to put it in? Is it a leaking radiator? Head gasket?
The previous owner of my old work truck thought he had a bad head gasket (it was a valve guide seal), and he put bars in there. It turned everything sludgy as heck, and 2 years later, after two flushes and a water pump replacement, the coolant was STILL sludgy and discolored, and probably led to the water pump failure.
My personal opinion is don't use it unless you really have to, like to try to stretch some more miles out of a bad head gasket.