MMS

hi everyone

I picked up a 2011 E550 cabrio and I'm catching up on some maintenance and fix tasks. Now I'm ready to tackle spark plugs. the car has 99k miles on it and There is no record of the plugs ever being replaced (it may have happened at an independent shop)

my questions
​​​​​​- Is it really necessary to change the coils with the plugs at this mileage? (mechanic wants me to)
- does this car require changing the wires also with some frequency?
- would the car benefit from ngk iridium plugs or should i still to oem/recommended platinum

thanks
M

Chevota

My guess is the coils have been replaced already at some point. Coils are weird, they should last forever but clearly, somehow, designed to fail prematurely. The wire should come with the coil. If it were me I suppose Id buy one or two to keep on hand for when one fails. Up to you.
Plugs I cant say, but the oem should be more than fine.
I replaced my orig plugs at 60k and it made zero difference. I didnt expect it would, but somehow I was dissapointed anyway. Ive never worn out a plug, and 99% did not have a fancy tip. Ive seen pictures of them, but not sure how they manage to do it. When they cause problems, for me, its always fouling and fancy tips do nothing for that.

loneryder

Highly recommend OEM plugs. They are designed to to be indexed correctly when installed. It's very important in these engines.

Nyshadow

OEM Plugs and coil packs are Bosch correct?

MMS

in my case (e550 2011 cabrio) the mechanic told me the oem plugs he had were ngk

chassis

Changing coils makes a difference. MB does not specific a coil replacement interval. I do it on my cars. Coils degrade over time and are therefore a wear item. 75k miles is my target replacement point for coils.

For MB coils specifically, the assembly grease used by the factory dries to a hard glue like consistency and makes coil removal difficult without damaging the boots. Another reason to replace them. Use a liberal blob of dielectric grease in the boot to aid disassembly at the next spark plug change.