2003 Mercedes C-Class Owner's Manual - Page 336

Technical data Fuels, coolants, lubricants etc. Coolants The engine coolant is a mixture of water and anticorrosion/antifreeze, which provides: Corrosion protection Freeze protection Boiling protection (by increasing the boiling point) The cooling system was filled at the factory with a coolant providing freeze protection to approximately -22°F (-30°C) and corrosion protection. If the antifreeze mixture is effective to -22°F (-30°C), the boiling point of the coolant in the pressurized cooling system is reached at approximately 266°F (130°C). The coolant solution must be used year-round to provide the necessary corrosion protection and increase boil-over protection. You should have it replaced every 15 years or 150000 miles (250000 km), whichever comes first. Coolant system design and coolant used stipulate the replacement interval. The above replacement interval is only applicable if MB 325.0 anticorrosion/antifreeze solution or other Mercedes-Benz approved products of equal specification (see Factory Approved Service Products pamphlet) are used to renew the coolant concentration or bring it back up to the proper level. To provide important corrosion protection, the solution must be at least 45% anticorrosion/antifreeze [equivalent to freeze protection to approx. -22°F (-30°C)]. If you use a solution that is more than 55% anticorrosion/antifreeze [freeze protection to approx. -49°F (-45°C)], the engine temperature will increase due to the lower heat transfer capability of the solution. Therefore, do not use more than this amount of anticorrosion/antifreeze. If the coolant level is low, water and MB 325.0 anticorrosion/antifreeze should be used to bring it up to the proper level (have cooling system checked for signs of leakage). Please make sure that the mixture is in accordance with label instructions. The water in the cooling system must meet minimum requirements, which are usually satisfied by normal drinking water. If you are not sure about the water quality, consult your authorized Mercedes-Benz Center. 336