The glycol in anti-freeze never wears out unless it's been overheated. The corrosion inhibitors simply go away with time. With the price of anti-freeze being what it is, I'm starting to drain it every five years or so, filter it, and add this schmoo or something similar.

Cooling Sytem Corrosion Inhibitor


"We live in a time when intelligent people are being silenced so that stupid people won't be offended".