While I have the block heater and cord installed I do not ever use them. I have started the '99 in -30 degree and colder weather easily by simply glowing and using Mobile 0W40 or Rotella T6 5W40 synthetic oil

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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