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NGK vs Bosch vs Mercedes branded?
Kinda confusing? Also, is it necessary or recommended to change the connectors? I see FCP Euro sells all 3 brands and the connectors. I did review the thread about indexing. Looking for feedback on which brand to use. Is replacement recommended at 50k miles not age? Car is 10 years old with 35k miles. No performance issues. Thanks.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Personally, I would go by mileage. Plus, the stock plugs are iridium plugs which generally are good for 100,000 miles. That said, I went with NGK for the SL as they are OE plugs. Mercedes Genuine plugs are made in Japan, as well as, the NGK.
I went with the Bosch ones from FCP for my 2013 550. It has 59k on it. My local Indy said he doesn’t change the connectors unless there is an issue and they are readily available locally if there is a problem removing them. He also said to make sure to torque to 23nm so the plug lines up properly. I am not sure if that is needed on your engine. I did get the plug socket with the swivel head. Apparently it is a little tricky to get the correct angle on some of the plugs with the socket extensions. I may tackle this project this weekend or next.
I'm led to believe that the time restriction is there to stop the plugs seizing in the head, which can, apparently, happen over time. I changed mine every four years (V8) and use mercedes plugs as there is little difference in price (in the UK) to non mercedes items.
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by Bigpoppy
...He also said to make sure to torque to 23nm so the plug lines up properly. I am not sure if that is needed on your engine...
There is some disagreement over the requirement to index the plug with the injector depending on if the engine uses stratified combustion (DES) or homogeneous combustion (DEH). M276 engines in the US use homogeneous combustion where the orientation of the spark plug is not critical. In non-US cars, stratified combustion is used for emission purposes and orientation is critical. To simplify proper installation of spark plugs world-wide, 23Nm is the specified torque. NOTE: The DES and DEH specification for engines was stated in a technical report dated 2010, before the M276 bi-turbo was produced, and I have found no updates. Therefore, I index the spark plugs to both my cars out of caution. Also, there is no distinction for the M278 engine, which was turbocharged from the beginning and is assumed to use stratified combustion. Therefore, maybe turbocharging results in or requiresstratified combustion. Play it safe and index your spark plugs.
Last edited by JettaRed; Mar 28, 2025 at 10:32 AM.
I changed my plugs earlier this year in my 278/TT. I posted my issues in the other spark plug thread. I could not get the NGK to index properly, so I switched them to the MB plugs. All of the MB plugs indexed properly with no problems.
I use NGK in many of my engines. (i.e. boats, off road toys, etc). I have had great results with them, just couldn't get them to index in my car. Just an FYI.
I changed my plugs earlier this year in my 278/TT. I posted my issues in the other spark plug thread. I could not get the NGK to index properly, so I switched them to the MB plugs. All of the MB plugs indexed properly with no problems.
I use NGK in many of my engines. (i.e. boats, off road toys, etc). I have had great results with them, just couldn't get them to index in my car. Just an FYI.
Hmm? I may reconsider my choice. Did you buy your plugs at a MB dealer? Is this the plug your bought? I see you have an different motor. I have the M276 so the plugs may be different.
@rmorin49 I bought my plugs at FCP Euro. It could be the difference in the M278 vs M276. I'm going to change the plugs in my wifes M276/TT in a few weeks and I'll get the NGK plugs for it. I know @JettaRed used them in his M276 with no issues. I have no idea why the NGK didn't index in my M278.
@rmorin49 I bought my plugs at FCP Euro. It could be the difference in the M278 vs M276. I'm going to change the plugs in my wifes M276/TT in a few weeks and I'll get the NGK plugs for it. I know @JettaRed used them in his M276 with no issues. I have no idea why the NGK didn't index in my M278.
The Mercedes branded plugs are considerably more expensive. Are they German or Japanese?
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Originally Posted by TinManMike
I changed my plugs earlier this year in my 278/TT. I posted my issues in the other spark plug thread. I could not get the NGK to index properly, so I switched them to the MB plugs. All of the MB plugs indexed properly with no problems.
I use NGK in many of my engines. (i.e. boats, off road toys, etc). I have had great results with them, just couldn't get them to index in my car. Just an FYI.
I had the opposite experience with my car. I tried the Bosch (no MB logo) and could not get them to index. The NGKs indexed perfectly.
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