SL/R231: 2017 SL450 Spark plug Replacement
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Newbie
Joined: Apr 2023
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From: Atlanta
SL450
2017 SL450 Spark plug Replacement
I have a 2017 that I want to change the plugs on, but I really don't want to screw anything up. I don't fully understand what indexing is and how to be sure it is correct. Is there a tutorial video that anyone is aware of? I can't find any that are specific to the 2017 SL or any R231 for that matter.
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From: Colorado
G550
One of the forum threads on the topic of indexing is at https://mbworld.org/forums/c63-c63s-...-indexing.html. I recently purchased a set of MB plugs (p/n 0001590500) and checked them for consistent ground electrode orientation which would be prerequisite for ease of indexing.
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
I have a 2017 that I want to change the plugs on, but I really don't want to screw anything up. I don't fully understand what indexing is and how to be sure it is correct. Is there a tutorial video that anyone is aware of? I can't find any that are specific to the 2017 SL or any R231 for that matter.
I want to change mine at some point as well, so be sure to let us know how it went.
Good luck!
Last edited by hornethandler; Sep 15, 2025 at 06:19 PM.
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From: Hagerstown MD
2015 SL400; 2019 X5M40i
FCPEuro assured me that the Mercedes branded plugs WILL index perfectly IF they are torqued properly. YMMV
I plan to replace mine around 50k miles even though I think they would be good to 100k.
I plan to replace mine around 50k miles even though I think they would be good to 100k.
Last edited by rmorin49; Sep 24, 2025 at 06:05 PM.
Joined: Nov 2016
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From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
MBWorld Fanatic!
Joined: Dec 2015
Posts: 1,636
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From: Hagerstown MD
2015 SL400; 2019 X5M40i
Never quite understood why mercedes recommends changing the plugs as soon as they do since most other manufacturers suggest 100,000 miles when using Iridium plugs (which mercedes uses). The only semi-reasonable explanation is that Mercedes is concerned the plugs may suffer galvanic corrosion (or whatever it is called when aluminum adheres to steel).
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Joined: Jan 2019
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From: Philadelphia area
2014 SL65 AMG, 2018 S560
Yes, specified torque is the key to proper indexing according to MB. Related to that, make sure the seat around the plug opening is clean before putting in a new plug.
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MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,156
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From: Colorado
G550
Never quite understood why mercedes recommends changing the plugs as soon as they do since most other manufacturers suggest 100,000 miles when using Iridium plugs (which mercedes uses). The only semi-reasonable explanation is that Mercedes is concerned the plugs may suffer galvanic corrosion (or whatever it is called when aluminum adheres to steel).
