I have gone through several pages of old thread and the only thing mentioned is Bar's Stop Leak products. Within the thread there is a 50/50 response of wether or not to use it. The application is a 20 passenger van/bus that some of my friends are using as a vehicle for their apartment ministry, and a homeless ministry. They move people in and out of apartments for free, and they help feed the homeless. Lots of furniture and lots of chests of ice and food will be carted around Dallas in this very large van. They were "given" this van by someone's father who had it sitting in a pasture for the past 10 years. My friends are good guys, just very broke. I don't want to push them down the wrong path. I just got a call that it has a small leak in the radiator, they drove it into town last night from somewhere out in west Texas and it lost around 2 gallons of coolant along the way. It held around 170 degrees, I dont know how they got that number, and it did not overheat on the way here. Nobody has the cash right now for a new radiator. Although I probably should shop around junk yards and e-bay for one. What additive would yall reccomend if any?