Originally Posted by nhdoc

Mercedes recommends that you use the M-B brand GPs, not aftermarket. I don't know if anyone has done a comprehensive comparison of the OE V OEM GPs to see if there is any difference. Maybe there is, maybe not. The OE plugs I used were made by Bosch but I don't know if they are 100% identical to the same Bosch plugs you can buy from Pep-Boys. I suspect they are.

It does seem odd that after all these years Mercedes hasn't worked with the vendors to help develop a stronger plug design that doesn't break. I'm sure if you as Mercedes they will blame the plug vendor and if you ask the plug vendors they will blame the head design for conditions that cause the plugs to get stuck...no German makers ever admit they ever made anything that wasn't perfect