In preparation for an upcoming spark plug refresh for my car this weekend, I decided to survey in advance the most well-known options. Starting point was the BoschUSA auto parts website, with its "Vehicle Finder." Here's what Bosch says is available for a 2005 E55:



Here's the well-known FR6MPP332 plug:



And here's Bosch's new Iridium "9652" plug:



Next is the MB factory spec NGK ILFR6A:



And last is the LFR6AIX-11 IridiumIX plug:



The NGK website says this about the standard MBUSA plug:



And praises the "IX Iridium" plugs:



Here's a shot showing the plugs side-by-side:




Oops!!! That new Bosch Iridium plug (9652) that the Bosch website says fits our engine is the "short reach" variety that has been discussed many times before. In a nutshell, the plug won't extend sufficiently into the combustion chamber of the head. So I'm passing on this one.

With the hype at the NGK website, I bit and decided to try their "IX Iridiums." My car's engine isn't modded enough to justify a colder heat range, so I'm going with the NGK LFR6AIX-11 plugs. At about 6 years and 85K miles later, my engine is undoubtedly ready for a set of fresh plugs. Should be fun; the wifey will be out of town so I'm down for some quality time working on the beast - without interruption(s).

 

it is a easy job, make sure you have a swivel spark plug socket. Use anti-seize compound on the new plugs.
Remember lead from top connection of the coil goes to the first plug

 

I always run those NGK Ir plugs. Never an issue.

 

Thanks, I shoud have done this when I had the headers out - but I didn't.

Does anyone still use a little dab of dielectirc grease in the plug wire boot?

 

What is a good source for the NGK LFR6AIX-11 plugs? I will be doing these in a couple of months... Anything better than Amazon.com at $7.55 per plug with free super saver shipping?

 

Does the gap vary by the type of plug used? If you go to NGK's website, it says the gap is 0.039 for a 2006 E55... I always thought it was 0.032????

 

And bought the MB NGK plugs for the M113k engine for my 05 CL55. I have found an increase in gas mileage since the change at start and on the highway. The original MB NGKs in the block were in surprisingly good shape, none the less.

At the time the 9652s were not available and the over the counter NGKs seemed subtly different in the insulator as the pics show. I do not understand what difference it makes, so I bought the Parts from MB and paid the premium.

Thanks for the pics. I suggest you repost this (or whatever the forum rule is) in the Tech Thread for the M113K, please.

This thread seems definitive. Thanks Komp55 for the great work!

 

Yes, I sourced the NGK LFR6AIX-11 plugs from here:

http://ngksparkplugs.ecrater.com/p/2...idium-ix-spark

He also stocks the colder LFR7AIX-11 plugs as well. Very fast shipping; all in with shipping was just under $108 for all 16 plugs needed.

 

I use the colder LFR7 and it works wonderfully.

 

komp55

whats the mileage you have on your car? I'm at 60k and will probably do this when temps cool down a bit in Oct.

 

Mine's at 85K with its original plugs.

 

thanks for the info. Wondering if i should hold off and wait, but it is 6yr old now and the maintenance interval says 5yr/100k miles i believe.

 

Can anyone verify the correct spark plug gap? or does it vary by spark plug brand?

 

Thanks for the write up - A lot of info on plugs.

The car runs fine, I just plan to change the plugs this fall because the plugs are 6yrs old.

 

Especially if you are making another 150rwhp!

 

I have my manual in front of me (2003 E55) and it calls for .039 gap. Hope this helps.

 

I went a step colder to the LFR7's from NGK as well, even prior to adding mods as at the time of installation I knew I would be adding more boost. Never had an issue. I was told that the NGK's should not be gapped, as they are supposed to come pre-gapped to spec.

 

Why is it that the NGK website is not saying that the 6619 plug is for the E55?

 

Can someone please confirm that this plug is not the right one and that the NGK plug above is correct.

This is from the JEGs website.
BKR5EIX-11

Thanks

 

This is a link to the NGK website, showing the 6619 as an application for the W211 E55.

http://www.ngksparkplugs.com/part_fi...engineid=31950


So yes, it's definitely one of the correct plug alternatives.

 

Thanks for that info.

 

My local dealer is saying his "book" shows 3.0 hours to replace the plugs on my 2006 E55. Is that true? What has to happen that it takes 3 hours?

 

It should not take more than 1 hour. The other 2 hours they take coffee break and enjoying road testing your car.

 

I just ordered the spark plugs (ILFR6A) from amazon. Total was $154.80 delivered to my door. I will be replacing them this weekend. Don't expect it to take more than a couple of hours. I called the stealership just to get an estimate and was quoted below.

Parts: $292.00
Labor: $520.00

Total: $812.00

Not only that, I also ordered the supercharger and the v-belt from primeparts. Cost me total of $88.00 delivered. Dealer quoted $314.00 total.

So if I went with the dealer, the total cost would've been $1126.00. BIG Thanks to mbworld AND the folks that have posted the DIYs, it'll only cost me $242.80 and a few hours on Saturday.

 

My indy replaced mine last week with ngk laser iridium and also did the motor mounts and transmission mount for a total of $760 parts and labor. Didn't think it was too bad and was glad to give the business because he was very appreciative.