We're talking plugs, not plug wires, right?

The plug wires require either the special MB tool (or a pair of pliers, in a pinch) for removal. Otherwise you can break the holder(s).

And yeah, over a several-thousand mile period, the differing alloys of the spark plug and cylinder head coupled with heat creates a chemical reaction that essentially "welds" the plugs to the head...hence the herculean effort required to remove them!

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car