Coolant concentrate does more than protect from freezing: its inhibitors manage electrochemical reactions between aluminum, cast iron and solder. A lesser-known pitfall is mixing with tap water. Hardness salts can neutralise inhibitors and deposit on hot surfaces, narrowing passages and lowering heat transfer. In Nordic stop‑go and long highway pulls, small deposits can push a marginal system over the edge. If you dilute concentrate, use demineralised water and keep the ratio consistent. The same logic helps washer pumps and jets too. For a simple option, see Technical Distilled Water.