rick hesek

Hi all,
My 09 CLS550 service interval chart recommends the spark plugs be replaced at 80k miles (or 8 years). No additional replacement interval and the chart goes to 150k miles. There is also no recommended replacement for the ignition coils.
I am going to replace my spark plugs since I am at 120k miles and I wanted to hear what comments I might get from this group.
My inclination is to also replace the coils since their resistance can degrade over time, heat, cold and use.
The car is running well and no indication of a fouled plug or bad coil. I drive this car like it's an F16 fighter jet, only faster.

Thanks,
Rick H

localmechanic

On older euro vehicles, I always replace the coils when servicing plugs.
If the plug had evidence of carbon tracking, it will come back if you reuse
the same rubber boot of the coil

konigstiger

As recommended, plugs/coils. To clarify MB recommends every 80,000/8-years (whichever comes first) so next change would be 160,000/16 years.

rick hesek

That is what I figured.
Thank you!

Rick H

rick hesek

Done.
I went with NGK plugs (PLKR7A), vs Bosch, due to feedback here. Besides, I have had great success with NGK's in other cars. I went with the Delphi OEM coil.
The job took 1 hour which included pulling all the necessary tools together, checking plug gaps and unpacking new parts. No issues, but I did find all of the original plugs were not much more than hand tight. These were replaced at 80k miles by a local dealer.
Acceleration response has noticeably improved. Engine runs smoother and quieter, also. I'm guessing one or more original coils were degraded. Plus the plugs are tight now.

Rick H

2006C230V6

Congratulations on a successful project. It's a good feeling when you've done the work yourself. I decided to go with the stock MB plugs which were $15ea at our local dealership. I understand they are also NGK, but the OEM really is a beautiful plug. It's a shame no one will ever see them after they are installed.
I sat one on my desk at work until I had to install them.

Dnasty

Funny, I was literally about to post this as my car is at around 93k miles and I don't think the previous owner replaced the spark plugs (bought it at around 80k miles). Where did you order your spark plugs from?.. Did you torque them etc? I was looking at ngk but theres so many friggin options not sure what to chose.. There's also the oem mercedes which i am not sure who manufacturers it. Also what is the difference between the resistor style and the regular style plugs. Any other maintenance people do around this mileage like transfluid flush?

rick hesek

Cool! It sounds like you really like your car. As you should!
I bought my NGK plugs on eBay and spent about $8 each. They retail for @ $15. I have had no issues with NGK in any of my past gas Mercedes. The larger engine cars seem to reject Bosch plugs, for some reason.

Have fun!

rick hesek

I believe there are only 2 spark plug options for these engines. Bosch and NGK. I have had better success with NGK and it goes back to my 2002 S430 (2 plugs per cylinder), 1983 380 SEC and my 1987 560 SEC.
I bought my current plugs on eBay. I think I paid about $8 each which is about half retail.
If you go to the NGK part application site, you will find the correct plug for the CLS500.
https://www.ngksparkplugs.com
I did not torque my plugs. The NGK have a crush ring, which collapses under the end force, and creates a seal. By feel, you can tighten the plug to where this crush ring collapses. There is noticeably more torsion resistance which is when you stop tightening.
Clear?

Rick H

rick hesek

I believe the earlier CLS500's have different service intervals. Check here again for your specific car. I attached mine here:

Rick H

Dnasty

That's pretty cool.. thought i would have to get a special angled torque wrench to do this but this should be a pretty easy job. Their site recommended the NGK PFR5R-11.. wondering why they recommend different plugs for your 2009?

konigstiger

06 cls”500” has 113 engine, 09 cls”550” 273 engine.

Dnasty

I just did this... you guys inspired me and my car is at 93k so I figure it's due for it. Car seems to be running gutsier and I notice acceleration improvement, it also sounds better. On the downside I also noticed that oil appears to be leaking from my valve cover gasket mainly on my driver side and the old spark plugs I pulled out had this thick syrupy dark brown gunk on it... is that oil? Guess I found my next job... is it an issue that I put new spark plugs in when there's a valve cover gasket leak or should I just aim to get this done soon. It's not a huge leak but it's definitely leaking. I also noticed more of this brown syrupy gunk on the engine cover as well.. not really sure what it is.
On a side note i'm looking at an email I got from benz dealership they wanted $867 to change spark plugs... hah.