Green coolant, especially if not changed every other year, will lead to severe corrosion of both the aluminum radiator AND the aluminum heads. On my sister's Volvo 740 Turbo, the head corroded through around a couple of cylinders, causing the head gasket to blow on the highway. New head and rad, about $700 in parts.
Use only the MB or Zerez G-05, green coolant will NOT protect against corrosion of the aluminum.
I'd avoid DexCool types, as the anitcorrosive additive is silcate, and that will result in the deposition of silicates of various sorts on the rad and in the block and head -- these are NOT soluble in any sort of coolant flush you would want to put in there, and cannot be removed.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!