You are removing old (depleted) coolant and adding "fresh" coolant with fresh additives (lubricants and anti-corrosion) Rather than a full drain and refill you are doing a partial drain and refill.

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1999 Mercedes E300TD daily driver sold at 238K miles 106K miles were mine, rust worm got it :-(
2006 Mercedes CDI new daily driver! 56,000 miles May 2016 now 85,625 Apr 2018 and Apr 2019 101,000 miles Apr 2020 109,875. March 2024 135,250, Dec 2024 145,000 miles