2012 Mercedes S550 W221 M278 - Spark Plugs

2012 Mercedes S550 W221 M278 – Replace Spark Plugs and Wires

9/7/2024

My Mercedes is 12 years old. I’ve owned it for 9 years.
I bought it with about 30,000 miles, and now it has 115,000 miles.
It was way overdue for spark plugs.

I actually bought the plugs a year ago, and the price has gone up $10 since!

You have to remove the air filters to get to the spark plugs. I made a separate video to cover replacing the air filters.    • 2012 S550 Mercedes - change air filter  

You’ll need to have a decent collection of ratchet extensions and swivels, to find the best combination that will work for you on the spark plugs and coil bolts.

The WORST part of changing the plugs was pulling off the plug “wires”, which aren’t really wires.
I spent an hour on the plug wires alone. I got really tough on them.
The “wires” stretch ¾” to 1” before they pop off.
I broke at least 3 of the “wires”, before I figured a fairly reliable way to pull them off the plugs.

I made a separate “Forensics” video showing the cross section of the plug “wires” and how hard they are to pull off the plugs and the effect of dielectric grease. It’s not a wire at all; there’s an aluminum rod and a couple springs inside the rubber boot cover:
   • 2012 Mercedes S550 W221 M278 - Spark Plug ...  

I decided to replace all the “wires”, and fortunately I found 8 of them at RockAuto.
STANDARD MOTOR PRODUCTS SPP184E.
Mercedes OEM number - A 276 159 00 42. A2761590042.
RockAuto $40 delivered:
https://www.rockauto.com/?carcode=150...

Bosch Double Iridium Spark Plugs OEM GERMANY ZR6SII3320 Benz 0041598103. Ebay $63 +tax delivered:
https://www.ebay.com/itm/174735018856

These are the boot pliers, that didn’t work for me. For you? Maybe. Amazon $16:
https://www.amazon.com/gp/product/B01...

Thin wall, 12 pt spline, spark plug socket. eBay $10;
https://www.ebay.com/itm/314435378998...