Just got an 88 300e that was maintained meticulously. Radiator appears original.

It had the green stuff in it... i drained and flushed and flushed and flushed..

...based on the readings on this board i bought zerex at 9.99 a gallon. I think the green stuff was 8.59.

It was a pretty easy decision to switch over. did the thermostat at the same time just for preventative maintanence. I typically change my radiator fluid every three years.