2007 Mercedes SL-Class Owner's Manual - Page 451

Technical data Fuels, coolants, lubricants, etc. 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 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 an authorized Mercedes-Benz Center. 450