Correct answer
Raise the temperature at which the coolant boils.
It raises the coolant’s boiling temperature compared with the same liquid at lower pressure. This helps prevent boiling within design conditions; it does not guarantee that boiling is impossible or impose a universal optimum temperature of 120°C or below 80°C. The value depends on pressure and coolant composition. Follow the manufacturer’s coolant, cap and maintenance specifications. Never open a hot, pressurised circuit: pressure release can cause boiling and liquid or steam discharge with a burn risk.
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Raise the temperature at which the coolant boils.
Always set every engine’s optimum temperature to 120°C.
Make coolant boiling impossible under every condition.
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