Some people feel that the W210s run best on single electrode BOSCH or equivalent NGK plugs. Basically what was in it when new. About 18 mos. ago I switched to BOSCH 2 electrode Platinum plugs and have noticed no difference in performance or gasoline mileage which I check on every tankful. As always YMMV

FYI, newer plugs no longer require any anti-seize compound as there is a coating on the plug.

Good luck.