No need for the H9DC0....though my dealer still has them for about $3.20 apiece....

I just use NGK resistor standard style plugs, they work great. Car runs smooth and strong, and has been getting between 21 and 25mpg. (300E) I've had them in for many thousands of miles now. 0 issues at all. About $16 for a set of 6

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)