A good deoil agent (simply a surfactant) which is cheap is PhotoFlo. Half of a small bottle would completely flush the system quite well. It is a very strong surfactant but also leaves almost no detectable residue (it can't or else we'd have stains on our photos.) After that, the vinegar or citric flush.
I switched to the factory recommended stuff last fall and haven't looked back. The coolant is still nice and slightly blue after all this time. No rust seen after I flushed with a hose then flushed using gravity and a lot of distilled.

Phil Forrest

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1972 220D "Trudy," named by a friend.

"The 220D sounds good... I suspect it is the only car that you need a calendar for, rather than a stopwatch, when doing acceleration tests."
Tom Abrahamsson