My TDI has a very long after glow, sometimes lasting over 5 minutes at full voltage. When I replaced the plugs last winter they had 150,000 miles on them and they all still got hot.

I assume the ones on my SDL are original, and have 56,000 miles on them. The afterglow on that car lasts just a short time, I think 45 seconds is the maximum under extremely cold conditions?

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.