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Again just to share my experience. First of all it’s a straight forward job once you get going. Biggest issue i had was to take the spark plug boots off. I realized that doing it on a warm engine did the trick. The problem is the old dielectric grease that is dried out. When the plugs are warm the grease softens up and the boots come off nice and easy. Alright, once the boots are off, it’s a peace of cake. 14 mm thin wall 3/8 drive deep socket and a 6 inch extension and off you go. Before you install the plugs lightly grease the ceramic with dielectric grease and also the inside of the boot with a q-tip. Make sure you don’t put grease on the connection. Make sure the gap is at 0.028 inch. Re-install and torque the plugs to 23 Nm. Re-install the coil pack and torque to 9 N.m. Re-connect all coil packs and re-install the air intake and filters. Original spark plug maker and type. NGK SILZKFR8G7S Laser Iridium. By the way don’t go crazy on replacing those. Again MB just wants to make money with you and their maintenance intervals are way too narrow. As per NGK the spark plug longevity is 100000 miles. See https://www.ngk.com/ngk-96427-silzkfr8g7s-laser-iridium-spark-plug. See also attached a picture of my spark plug after 107000 km or 67000 mi.
It's not the life of the plug, but as you found out, they get hard to remove. There is an awful lot of thread contact with the head, as your photo shows. The only compression seal is at the top of those threads, a long way away from the combustion chamber.
Removal without damaging anything is more important than getting the maximum life out of the plug.
I was under the impression that Mercedes doesn't use anti-seize at all with the initial engine build, but that may be incorrect.
Either way, go with Mercedes recommendations, not NGK.
Thanks for your input…I’m curious to know what made you think that MB used anti-seeze. It looks like there was nothing on the threads which is the way i re-installed. Dry. Hope i do t have to remove again.
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