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Will be working on a 2016 e350. Have done some search regarding the spark plugs and it seems they need to be "indexed"
Have done some online search and watch some vids and they all have mixed information.
One thread in particular were the OP was stating that both the Bosch plug and the OEM were not being able to index correctly.
So I went ahead and bought one OE spark from dealer and 6 from auto part store. OE is indeed a Bosch plug. The part number on the box is different but on the plug is very similar. OE number on plug is Z6SII3320R and Auto part store Bosh plug number ZR6SII3320. The difference is on the R placement.
Physically they look identical with just one difference in the electrode tip. As for the threads they both seem to match and thread starts at the same point. Washers also look the same. They both have the Bosch logo stamped.
So why wouldn't the Bosch index if oe suppose to index? We will see. Have you had issues indexing Bosch plugs?
Last edited by JCAuto723; Jun 9, 2023 at 09:02 PM.
Update: Just finished the job. All 6 OE spark plugs were torque/indexed at the 9 o'clock position. New Mercedes OE will torqued/indexed at the same 9 o'clock as well as the new Bosh set.
So either Bosh or Mercedes torqued down at 17lbs and send it. They will not index between 10 to 1 o'clock. And honestly the reason they came out with that bulletin is perhaps the ngks are indeed different or they just want you to take it to the dealer.
Update: Just finished the job. All 6 OE spark plugs were torque/indexed at the 9 o'clock position. New Mercedes OE will torqued/indexed at the same 9 o'clock as well as the new Bosh set.
So either Bosh or Mercedes torqued down at 17lbs and send it. They will not index between 10 to 1 o'clock. And honestly the reason they came out with that bulletin is perhaps the ngks are indeed different or they just want you to take it to the dealer.
Maybe there are fake Bosch plugs out there or maybe it's random whether you need to index them or not depending on what batch you get. There are other threads out there where people have bought Bosch plugs and they didn't index correctly,.
Maybe there are fake Bosch plugs out there or maybe it's random whether you need to index them or not depending on what batch you get. There are other threads out there where people have bought Bosch plugs and they didn't index correctly,.
There are threads where they "can't" index OE plugs too. I believe it's a bit of confusion and error on the install or explanation/understanding. Unless they just want to index them at 12 o'clock and that's just no way possible unless you get a thinner washer. But I don't see a need to do that. Again this is most likely a way on getting consumers to get the vehicles into the dealership.
The manifold doesn't need to come off and this is a less than two hr job. In fact once you get to do several I bet it can be done in less than an hour.
If I get a chance to do it again just for kicks I will get a ngk plug and try it.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
I have been working on cars and engines for over 50 years and never heard the term "indexing of spark plugs". Then again I have never worked on a F1 engine.
The reason I have never heard of it is because it is non-sense, or a polite way of saying total BS!
Indexing is done by placing (usually copper) washers of varying thickness on the spark plug shoulder, so that when the spark plug is tightened, the plug will rotate a certain amount, and gap will point in the desired direction. In most engines, performance will improve when the spark plug gap opens toward the intake valve(s). However, without testing different index positions in an engine on a dyno, it is nearly impossible to determine which index increases performance. Indexing spark plugs will typically make only a few more horsepower – usually less than 1% of total engine output. For a 500 hp engine, that’s only 5 hp. It is usually not worth the effort.
There are also drawbacks to indexing spark plugs. When washers are added, the spark plug may loosen if the washers don’t crush properly and hold the torque. Also, if too many washers are added, the firing end of the plug will not be as far into the combustion chamber and performance can decrease.
I would not waste even one second about indexing of spark plugs on your Mercedes.
I have been working on cars and engines for over 50 years and never heard the term "indexing of spark plugs". Then again I have never worked on a F1 engine.
The reason I have never heard of it is because it is non-sense, or a polite way of saying total BS!
Indexing is done by placing (usually copper) washers of varying thickness on the spark plug shoulder, so that when the spark plug is tightened, the plug will rotate a certain amount, and gap will point in the desired direction. In most engines, performance will improve when the spark plug gap opens toward the intake valve(s). However, without testing different index positions in an engine on a dyno, it is nearly impossible to determine which index increases performance. Indexing spark plugs will typically make only a few more horsepower – usually less than 1% of total engine output. For a 500 hp engine, that’s only 5 hp. It is usually not worth the effort.
There are also drawbacks to indexing spark plugs. When washers are added, the spark plug may loosen if the washers don’t crush properly and hold the torque. Also, if too many washers are added, the firing end of the plug will not be as far into the combustion chamber and performance can decrease.
I would not waste even one second about indexing of spark plugs on your Mercedes.
Just my $.02!
There's an old saying that asks if you have 50 years of experience or do you have 1 year of experience repeated 50 times? Indexing has been around for a long time. I used to do it on a turbo engine back in the 90's. If you remember JC Whitney, they used to sell the copper washers so you could do the indexing. And yeah, I don't think I noticed much if anything so didn't bother doing it more than once. On a 4 cylinder it was easy, you could mark the plug with the direction of the electrode and then see which way it faced once you had it tight and then use the right sized washer to get it correct. With Mercedes controlling the supply chain, they could spec out exactly how the plug was made so it indexed correctly and only one way when using the MB part. Maybe Bosch had a bunch of other ones that didn't meet the MB spec and worked for different cars where it didn't matter so those got tossed into a different bin. Eventually they try every trick in the book to get every ounce of power they can out of an engine. World War 2 had fuel injection but it didn't make to cars til decades later. You had waste fire where you got two sparks per cycle and now with MB's multispark, you get up to 5 sparks per cycle. Every little trick squeezes out a little more. If you didn't bother or care about it, you probably don't get the rated power out of the engine.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by cetialpha5
There's an old saying that asks if you have 50 years of experience or do you have 1 year of experience repeated 50 times? Indexing has been around for a long time. I used to do it on a turbo engine back in the 90's. If you remember JC Whitney, they used to sell the copper washers so you could do the indexing. And yeah, I don't think I noticed much if anything so didn't bother doing it more than once. On a 4 cylinder it was easy, you could mark the plug with the direction of the electrode and then see which way it faced once you had it tight and then use the right sized washer to get it correct. With Mercedes controlling the supply chain, they could spec out exactly how the plug was made so it indexed correctly and only one way when using the MB part. Maybe Bosch had a bunch of other ones that didn't meet the MB spec and worked for different cars where it didn't matter so those got tossed into a different bin. Eventually they try every trick in the book to get every ounce of power they can out of an engine. World War 2 had fuel injection but it didn't make to cars til decades later. You had waste fire where you got two sparks per cycle and now with MB's multispark, you get up to 5 sparks per cycle. Every little trick squeezes out a little more. If you didn't bother or care about it, you probably don't get the rated power out of the engine.
Yup I remember JC Whitney: Many parts including the aircraft landing light I put on my 1966 GT Mustang!
But back to the topic:
I have the 2019 E450 with 365 HP. At 80 miles per hour, approximately 20%, or 75 hp are used.
So you can take the time and effort to index your plugs to get an extra 3 HP or on the E350, an extra 2 HP, which you will never ever use. All that time and effort for nothing! And be sure that your torque those plugs correctly as well. An over or under torquing will change the position of your plugs!
As I posted, indexing plugs is non sense or a nice way of saying BS!
So you can take the time and effort to index your plugs to get an extra 3 HP or on the E350, an extra 2 HP, which you will never ever use. All that time and effort for nothing! And be sure that your torque those plugs correctly as well. An over or under torquing will change the position of your plugs!
As I posted, indexing plugs is non sense or a nice way of saying BS!
The whole point was that the MB plugs are already indexed, you don't have to do anything if you have MB plugs. Seems like maybe the Bosch plugs are indexed, maybe not. You just have to check. You basically put a mark on the plug to indicate which way the electrode was pointing and see if it lines up that way after they're installed so it's not too complicated if you're trying to save a few bucks by getting Bosch plugs instead of paying for MB OEM ones.
The whole point was that the MB plugs are already indexed, you don't have to do anything if you have MB plugs. Seems like maybe the Bosch plugs are indexed, maybe not. You just have to check. You basically put a mark on the plug to indicate which way the electrode was pointing and see if it lines up that way after they're installed so it's not too complicated if you're trying to save a few bucks by getting Bosch plugs instead of paying for MB OEM ones.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by cetialpha5
The whole point was that the MB plugs are already indexed, you don't have to do anything if you have MB plugs. Seems like maybe the Bosch plugs are indexed, maybe not. You just have to check. You basically put a mark on the plug to indicate which way the electrode was pointing and see if it lines up that way after they're installed so it's not too complicated if you're trying to save a few bucks by getting Bosch plugs instead of paying for MB OEM ones.
Have you looked at the where the spark plug is on the V6? Unless you can see into the spark plug hole, which is highly doubtful, you will not be able to align the spark plug.
Have you looked at the where the spark plug is on the V6? Unless you can see into the spark plug hole, which is highly doubtful, you will not be able to align the spark plug.
Again much ado about nothing!
It's not that complicated. Instead of marking the plug, you can mark the extension. Make sure it lines up before starting the plug and you can look at where the extension is once it's tight so you know where it ended up.
And it's Bosch not Bosh. Bosch makes the plugs for Mercedes but if you buy them directly from Bosch, they may have a batch that aren't indexed like the Mercedes ones. It's easy for them to do some QC after it comes off the line and to label one batch for MB and the ones that don't meet MB spec like the indexing get tossed into another bin and end up with a different label. But who really knows, maybe it's just trial and error. They can always do stuff after it's made, I like how Wahler is the OEM maker of thermostats, but if you buy a Wahler instead of a Mercedes one, the spot where there would be an MB logo has been ground out like someone's job was to take the ones they were going to sell direct instead of sending to MB and just grind out the logo.
It's not that complicated. Instead of marking the plug, you can mark the extension. Make sure it lines up before starting the plug and you can look at where the extension is once it's tight so you know where it ended up.
And it's Bosch not Bosh. Bosch makes the plugs for Mercedes but if you buy them directly from Bosch, they may have a batch that aren't indexed like the Mercedes ones. It's easy for them to do some QC after it comes off the line and to label one batch for MB and the ones that don't meet MB spec like the indexing get tossed into another bin and end up with a different label. But who really knows, maybe it's just trial and error. They can always do stuff after it's made, I like how Wahler is the OEM maker of thermostats, but if you buy a Wahler instead of a Mercedes one, the spot where there would be an MB logo has been ground out like someone's job was to take the ones they were going to sell direct instead of sending to MB and just grind out the logo.
Bosh Bosch same ****.
I highly doubt BOSCH has two different thread machines to produce the same sparkplug. Infact as just proved it with the pictures where it shows the threads start at the same point. Commercial retailer where I got them also clearly specifies that BoSCh plugs require indexing and torqued. Box also specifies the torque and not to over torque.
Have you looked at the where the spark plug is on the V6? Unless you can see into the spark plug hole, which is highly doubtful, you will not be able to align the spark plug.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
What does the R in a spark plug mean:
[R] Resistor - If an R is present, this indicates a resistor type spark plug. Resistor type spark plugs reduce the amount of radio frequency interference (RFI) that can cause ignition misfires and static on the radio.
I remember this from years ago. Mainly the radio interference on AM.
It says that even with 50 years experience, people can still be wrong and melted pistons can result. There’s a few threads on this exact subject of melted pistons and why.
It says that even with 50 years experience, people can still be wrong and melted pistons can result. There’s a few threads on this exact subject of melted pistons and why.
Thanks for posting: it is comparing apples to oranges:
From the post:
"In the picture, an NGK unapproved spark plug is compared to a Mercedes approved spark plug. The NGK plug does not have the correct thread length for proper indexing and it isn’t the correct heat range."
The article also points out that for indexing to occur, the correct torque must be applied to the spark plug. Good luck with that!
The article also points out that for indexing to occur, the correct torque must be applied to the spark plug. Good luck with that!
It's not really that hard, torque wrenches aren't that much money. You can pick one up at Harbor Freight for $20 or even a Craftsman is about $55 or you can go nuts with a Snap On and pay hundreds.
Thanks for posting: it is comparing apples to oranges:
From the post:
"In the picture, an NGK unapproved spark plug is compared to a Mercedes approved spark plug. The NGK plug does not have the correct thread length for proper indexing and it isn’t the correct heat range."
The article also points out that for indexing to occur, the correct torque must be applied to the spark plug. Good luck with that!
No, actually its comparing your very incorrect statements on indexing on direct injection engines to Mercedes statements on indexing direct injection engines. I, a normal person, was able to index with proper torque the first time I tried. Its not that hard (meaning very easy) and your info could be ruinous to anyone that reads it. The NGK statement has nothing to do with indexing correctly, but what will happen if you use a plug that is not correct and or do not index a stock plug correctly. Would you read the document and believe you can install a stock plug incorrectly, I think not. Cherry picking info does not reinforce your position. Im sure youre great at what you do, but please apply the information provided by mercedes on indexing and direct injection engines vs making up your own information to fit your own argument. Not trying to be negative towards you but provide proper non biased information to the readers.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by Baltistyle
No, actually its comparing your very incorrect statements on indexing on direct injection engines to Mercedes statements on indexing direct injection engines. I, a normal person, was able to index with proper torque the first time I tried. Its not that hard (meaning very easy) and your info could be ruinous to anyone that reads it. The NGK statement has nothing to do with indexing correctly, but what will happen if you use a plug that is not correct and or do not index a stock plug correctly. Would you read the document and believe you can install a stock plug incorrectly, I think not. Cherry picking info does not reinforce your position. Im sure youre great at what you do, but please apply the information provided by mercedes on indexing and direct injection engines vs making up your own information to fit your own argument. Not trying to be negative towards you but provide proper non biased information to the readers.
Touchy, Touchy, Touchy!
The article was comparing a non approved NGK plug with a different heat range, different size to a Mercedes, Bosch plug.
2019 E 450, 2016 E350 4matic (retired), 2018 Ford Edge Sport, 2008 Porsche Boxster
Originally Posted by cetialpha5
It's not really that hard, torque wrenches aren't that much money. You can pick one up at Harbor Freight for $20 or even a Craftsman is about $55 or you can go nuts with a Snap On and pay hundreds.
Again, you are assuming that after putting in the plugs, tightening the plugs with a socket wrench, the mechanic stops, puts down the socket wrench, goes for the torque wrench, then torques them and checks that the plugs are indexed and if not will take the plugs out and do it all over again.
As I posted, on a V6, where nothing is visible, good luck with that!
The article was comparing a non approved NGK plug with a different heat range, different size to a Mercedes, Bosch plug.
That is apples to oranges.
LOL, NOPE. YOU are plain wrong in your OPINION. You've already said proper torquing of the oem plug was stated in the doc and wished people good luck, implying you understand mercedes is saying to index their plugs correctly. Were you lying or are you just trying to be right while knowing youre wrong? Its ok to be wrong, and thats how people learn. Please nobody listen to this persons advice on indexing. Read the doc and determine for yourself....The document is not about NGK plugs, that is an example of a non oem plug not being able to be indexed. Im sure you can understand that,,,but youre proving you dont.
Im not being touchy. Im saving people from ignoring the facts and listening to you, endangering their engines. Its VERY well documented by people would have had melted pistons come across their work benches.
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