it has 165k on it. I have no idea when it was flushed last so I ended up flushing it. From what I was seeing the stop leak I had put in it was in the reservoir tank and completely covered the sides of it, it had an oil base but was sticky like honey. So i am thinking it was the cause of the brown junk along with god knows if the tank had ever been flushed prior to me owning it. I need a new sensor though cause the one in it is so gunked up its sad and even after trying to clean it, the low coolant still goes off. So now its just keping an eye on it. I hope its not my water pump I had that replaced not to long ago LOL