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I have not had time to read all of the page that TJ linked to, but in a short version:
The cylinder walls expand when the cylinder fires and then retracts. This causes small bubbles to form on the cylinder hall (coolant side) and it erodes (wears) the cylinder walls. The SCA changes the consistency of the coolant, making it form less bubbles and also coats the cylinder walls (coolant side) allowing the coating to be eroded instead of the metal of the cylinder wall. I hope this makes it less confusing. But maybe not.