I have 4 MB's. Three of them have the MB coolant. The fourth a 1984 300SD has had the green stuff since new. I just replaced the radiator after 350,000 miles and never had overheating problem. I could have had the upper tank gasket replaced since the core. upper and lower tanks including the necks were perfect.
I felt I got my moneys worth and installed a new one. According to my indy with 35 years dealer experience he feels the green stuff is overhyped. As for the green stuff cracking the plastic neck. In every case where the neck was cracked he said it was because the clamp was over tourqued.
Who knows what the real truth is.
1982 380 SEL (Euro)
1986 300E (Euro)