Has anyone heard of this stuff? It comes in a black pint sized jug and is a cooling system additive. It contains Nalcool which protects your cooling system from corrosion. It is very popular in heavy duty trucking. When I was involved in trucking we used this alot along with the test strips to test the active ingred. in your coolant. I used this in my 1994 Dodge Ram witha 5.9 and will tell you after 12 years the inside of the thermostat neck looked like new. You can get this stuff at any heavy truck dealer and it is recommended by CAT, Cummins and Detroit.(being reccomended by engine makers is a big plus, they dont endorse much). It will extend you coolant life forever, Pencool said it is great for auto coolants and is basically overkill protection. First thing they do when you have engine warranty trouble with a big truck is check the coolant