Originally Posted By: ted s
2001 mustang that came with basic green. i need to top off and cant tell for sure whats in it.
Just because its green does not mean its the old green coolant. Although its a good guess. I would do a fall, spring and fall drain and fill of the radiator with Zerex G-05 and then maybe go back to once every 2-3 years. G-05 will mix with the old green stuff if that is what you cooling system. However you will not get the true benefit of G-05 until the system is mostly G-05. A flush or complete drain would not hurt, but I am offering easier suggestions.