You cannot make antifreeze at home unless you have the corrosion inhibitors needed to prevent electrolytic corrosion between the aluminum and iron engine parts. The aluminum will corrode away (it becomes a soluble salt) and electric current is generated when aluminum and iron are connected by a conductive liquid.

MB coolant is the best to prevent this -- GM's DexCool type coolants have a tendency to precipitate silica particles, and that grinds up water pump impellers and seals pretty fast. Phosphate based corrosion inhibitors used in "cheapo" older style green coolants precipitate in the radiator, plugging it and the deposits usually cannot be removed, along with allowing severe corrosion very quickly.

Use the MB coolant, it's far cheaper than blowing a head gasket because the head corroded out around the combustion chambers (my sister's Volvo did just that -- huge holes).

Peter

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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!