Coolant isn’t just antifreeze; it also carries corrosion inhibitors and lubricates the water‑pump seal. A lesser-known point: color is not a chemistry code. Different makers may dye similar chemistries differently, and some reuse the same color across unrelated inhibitor packages. Mixing types can dilute protection or create soft deposits that settle in narrow passages after repeated heat cycles. In Nordic use with salted and slushy roads, cleanliness matters as much as concentration. If you aim for a long-life OAT approach, keep one chemistry and stick with it—the same principle applies to Longlife -36 °C Red.