Weird question. Does antifreeze get need to be changed like oil? I popped my rad cap and whats inside is this brown milky liquid. Now my truck doesn't overheat, doesn't burn oil, doesn't burn antifreeze. Is it possible its just dirty? What else could cause this? Also the antifreeze in the over flow take is green like it just came out of the jug, why aren't they the same color? Here's whats in there.