As part of the Winter/Spring maintenance (vehicle is currently in hibernation) I'm going to replace the thermostat on the M113 engine together with a list of other things to do and I was thinking of proceeding with the cooling system flush and replacement. What coolant should I be using? MB stuff or other type with MB approval? What is the correct fluid code for the MB coolant? I live in an area with very hard water. Should I fill and mix with distilled or filtered water? Thanks for any tips.