PeachParts Mercedes-Benz Forum - when to change spark plugs

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when to change spark plugs

I have to admit, I've never changed spark plugs since I've always had a diesel.
so, how do I inspect them for wear and gap them, etc. Plus where can I buy non resistor type locally.

The E320 just hit 90k so the 90k service is going down under my hands. It wont all get done today but it will all be addressed before the next tear off page in the service booklet.

Doing the oil today as well. I think I have a blackstone labs thing to send it out in for ha ha's

I think plugs are generally changed every 15,000km/9,000 miles.

At your interval, replacement is your only option, don't bother with trying to re-gap them. They should be changed every 15k. You want Bosch H9DC0...Try your local dealer as most online stores now only carry the resistor HR9DC0.

Every 30K with copper core plugs.

http://viewer.zoho.com/docs/mSbqL

this might be helpful

BOSCH Part # F8DC4
******** $1.48

I always use platinum plugs,and change every 100,000 miles.

Quote:

Originally Posted by M.B.DOC (Post 2464992)

Every 30K with copper core plugs.

That is what I am following with the 300E.....so I have about 21k to go on the current set. :D

ill try autozone for chits and giggle since I need to go dump oil after dinner.

Quote:

Originally Posted by TheDon (Post 2465280)

ill try autozone for chits and giggle since I need to go dump oil after dinner.

...they won'y have them. Dealer or ebay.

Is the Bosch F8DC4 a Non-resistor plug? If so, what is the difference of it between the H9DC0?

Quote:

Originally Posted by ps2cho (Post 2465563)

Is the Bosch F8DC4 a Non-resistor plug? If so, what is the difference of it between the H9DC0?

Yes, non-resistor. As there is no R in the part number.

I am currently running Denso T20EP-U in my m103s. NGK BP5ES's in my m116.

F8DC4
F=14mm thread (5/8" hex)
8= Heat Range
D=Thread Reach 3/4" Regular Electrode
C=Copper Core Center Electrode
4=Special Shell or Electrodes

H9DC0
H=14mm thread diameter Tapered Seat
9 = Heat Range
D=Thread Reach 3/4" Regular Electrode
C=Copper Core Center Electrode
0=Special Shell or Electrodes

Spark Plug Decoders:

Bosch:
http://www.not2fast.com/ignition/bosch_spark_plugs_short.gif

NGK:
http://www.not2fast.com/ignition/ngk_spark_plugs.jpg

Denso:
http://www.not2fast.com/ignition/denso_spark_plugs.jpg

Champion:
http://www.not2fast.com/ignition/champion_spark_plugs.jpg

So the F8DC4 run one notch "colder" than the H9DC0's...Under what conditions are colder/hotter sparks favorable?

Also, can you explain the last # in the part number (Special Shell or Electrode)?

Just trying to understand which would be best for me as it looks like this spark plug has a lot of sources compared to the H9DC0

I switched from the H9DCO's which were fouled to new Denso non resistor and I cannot be 100% sure, but I feel like it seems to be idling a tad rougher...That is why I want to get a spare set of Bosch plugs to test it out as the old ones I had were fouled up from past leaking stem seals.

Quote:

Originally Posted by ps2cho (Post 2465575)

So the F8DC4 run one notch "colder" than the H9DC0's...Under what conditions are colder/hotter sparks favorable?

Also, can you explain the last # in the part number (Special Shell or Electrode)?

Just trying to understand which would be best for me as it looks like this spark plug has a lot of sources compared to the H9DC0

I switched from the H9DCO's which were fouled to new Denso non resistor and I cannot be 100% sure, but I feel like it seems to be idling a tad
rougher...That is why I want to get a spare set of Bosch plugs to test it out as the old ones I had were fouled up from past leaking stem seals.

I cant speak directly to the conditions for hot/cold sparking, however this article from NGK might shed some light on it for you
http://www.ngksparkplugs.com/tech_support/spark_plugs/p2.asp

I also found another Bosch Decoder:
http://imgur.com/Lyy6S.png

So H9DC0 vs F8DC4

The 0 and 4 in the end seem to be:
4 seems to have an extended insulator nose
0 just says "deviations from basic version"
So I take that the 0's were the basic version and anything above that is an "enhanced version" which whatever the number corresponds to...

Thanks for the links.

Quote:

As the air temperature or humidity increases, the air density decreases, requiring a leaner air-fuel mixture. If the air-fuel mixture is too rich, decreased performance and/or carbon fouling can result.

As I live in Socal/Arizona in the future, the 1 stage from is between 80-100C cooler according to the chart, but still puts it within spec. Since I live in a hot climate, the colder plug should work fine. I will go ahead and order now I have some better information! If you live in a cold climate, you would not want a colder plug or you would be running even more lean.