Why was a cooling system additive used when car was serviced? Car Doctor

I had the radiator serviced on my car; just preventive maintenance. I noticed on the repair invoice I was charged for a cooling system additive.
Motoring USA on MSN

What your engine oil color is actually telling you

Engine oil color reveals its age, contamination level, and operating condition. Fresh oil is amber or light brown. Oil darkened to black but still translucent after a few thousand miles is normal.
Waste360

New Jersey Sustainable Fuel Changemaker The Fuel Ox® Announces Newest Addition to Innovative Additive Collection: Fuel Ox® Vantage™

New Jersey-based Sustainability Group (ISG) dba The Fuel Ox® has announced the newest member of its additive family: Fuel Ox® ...
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The Real Differences Between Diesel Engines And Gas Engines Explained

Aaron, a 27-year automotive technician and lifelong car enthusiast, attended Specs Howard School of Media Arts and learned the fundamentals of digital video and editing, shot composition and writing.