In the SoCal climate I use BP7ES, they are non resistor.
I higher number runs a bit cooler, to compensate for a warmer climate.
IMOP for NoCal BP6ES should be right.

 

The information is correct for Bosch (or other German plugs like BERU). The for M116/17 W-DCO or DC, or H-DCO or DC for M113 6 Cyl.
The DCO had a larger copper electrode than the DC and was made for MB.
With Bosch, the higher number means cooler running.
Here in SoCal I run Bosch W9DCO in the SEC and H9DCO in the 2.6.
All gapped a bit wider with .042
Even for those who like the smaller pre gap, its best to check the gap on all plugs, they are not as uniform as most of us assume.

Someone tried to tell me NGK uses a opposite scale for heat rating, its not true, and the same as Bosch etc.
http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml
Q: NGK Spark Plugs Heat Rating
The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The heat rating of each NGK spark plug is indicated by a number; lower numbers indicate a hotter type, higher numbers indicate a colder type.

I have run NGK BP7ES before and they worked well.

 

In the SoCal climate I use BP7ES, they are non resistor.
I higher number runs a bit cooler, to compensate for a warmer climate.
IMOP for NoCal BP6ES should be right.

Kind of true, the temp figure (normally the higher the number the cooler the plug)
is mainly due to the plugs performance in certain engines, i.e high perfromance engines need cooler plugs to alow for proper function and reliability, but climate is also a facto but not the main one. You should not run a resistor plug with the mercedes wires as theyve already got the correct resistance in the form of the supressor plug boot. Sounds like you need new engine mounts and to tune you idle mixture.

 

My
euro 1983 500 sec is running NKG BP5ES.
Do you think that may make her run hot?
I live in CA?

:bowdown:

 

I am planning on putting the 6ES in my 87 560SEL. Live in MN but car will only be driven in warm weather-stored winters. Is the gap figure I have seen correct?....042? Seems HUGE to me! Car is running okay but am adding some things and figured might as well do plugs too. But that .042 gap thing surprises me.

 

I just bought 8 of the BP6ES to change out the old sparkplugs with.

The terminal end of the old sparkplugs (the part the wire slips onto) removed was threaded and the spark plug wires easily clicked right into them. These new ones are not threaded and seem to have some kind of cap. Hopefully they can be removed, I'd imagine it's threaded underneath... They are incredibly tight though! As if a gorilla tightened them

Any ideas?

 

Just unscrew the caps, easy enough.

 

If only it were that easy. lol

These caps seem to have been superglued tight. I'll try to find a tool to unscrew them tomorrow

 

Do they really come with a "cap" pn them? Is it possible the wires have been changed and thus won't fit as readily on the new NGK plugs. I have not yet bought my NGK's and I note from a post above that the Bosch etc. plugs are also reccomended for the 117 engine. I am familiar with Bosch stuff and would use them.
But now even the spark plug issue is becoming confusing! LOL

 

Boy this plug debate gets bogged down at times and confuses the crap out of most particularly considering our situation re non resistance plugs required and then what heat range plug to use for individual cases??

This current Bosch spark plug Spec sheet is interesting
http://www.bosch.com.au/car_parts/en/downloads/Spark_Plug_Australia_Web.pdf

Down the back in the commonly asked questions section this is Bosch's answer to why they stopped producing non resistor plugs -
"Quote"
Q - Why no more non-resistor spark plugs?
A - Since they early 80's fuel injection systems have been designed by manufacturers to be fitted with resistor spark plugs. Fitting non resistor plugs in a resistor application can cause damage expensive components, affect overall performance and increase fuel consumption.
Resistor plugs can be fitted in non resistor applications.
Bosch recommends fitting a resistor type spark plug for every application.
"Un-quote"

Well that is interesting that they would quote that in writing!!

MB spec copper core ignition leads with the resistance built into the connector ends should all all test at aprox 1,000ohms +/- a few ohms when new no matter what the length of the lead and that is what the system was designed for.
The copper lead itself is multistranded and resistance for practible purposes is nil.
With older leads the conductor insulation is subject to continual heat and eventually breaks down. Old connectors can have resistance that increases anywhere up to 1350ohms which is getting into the heading for trouble zone.

End result in any sigificant increase in resistance on our system is a stuffed Ignition Control Module (EZL)

I fail then to understand at all why Bosch would recommend using a resistor plug in a W126 application - you are just asking for trouble.

That chart also gives a good rundown on understanding heat range and optimum plug for your application to ensure plug does not foul up (combustion heat too cold for plug to self clean) and at the other end of the scale where combustion temps are too high for the plug and it gets so hot it is pre-igniting the charge before the plug fires causing pinging and the resultant destructive damage that can cause.

3yrs ago under guidance of a local Mercedes Authorised Repair/service Centre the owner "who is also an old school Mercedes fanatic" told me the best now plug to run in our engines is "Beru Ultra-X UX79" Part # 0 002 335 600
BERU Ultra X and Ultra X Platinum ? the spark plugs for x-tremely high demands. | Federal-Mogul Global Aftermarket

So 3 yrs ago i purchased a set from him and "wow" i could never have been happier!!!
The high comp 500 engine has run perfect ever since from cold starts to highway cruising and hard driving pedal to the floor stuff to peak rev changes - never ever missed a beat and those plugs are still in the engine going strong now
I will never ever use another plug period

 

Boy this plug debate gets bogged down at times and confuses the crap out of most particularly considering our situation re non resistance plugs required and then what heat range plug to use for individual cases??

Yes it does and I am wondering if we are over-thinking the whole issue. I think it is safe to say that using non-resistor plugs are the way to go in most if not all cases...whether it be Bosch or NGK or whatever. As far as heat range goes stick with a plug that matches the original ones. Using my car as an example:
Original spark plugs were Bosch W9DC...no longer made but still available. The 560sl was shipped to all areas of the US (plus Australia and Japan). That means that cars shipped to Alaska, Arizona, Illinois, Florida and Maine all had the same spark plug. All way different climates and extremes.

Until I found a supply of the W9DC's I was using NGK BP5ES...popular choice on the 107 forum. Both non-resistor and both worked well in my car.

I can see where a different choice of plug might be the way to go on a modified or high performance engine. But for stock engines like mine I will stick to the original or as close to it as I can find.

 

From what I have been reading the spark plug heat is more dependent(has to be matched on the engine combustion internal temps )not the external temp.
External temps dif of tops 50 degrees winter or 40 summer are not likely to affect the internal combustion///maybe just the exhause manifold???

Be interested in that Beru Ultra.
Doesn't seem wise to skimp on plugs as they are a imp[ortant part of a engine.
:bowdown:

 

+ 1 on BERU. They used to make the perhaps best ignition wires as there was no outsourcing. The company was bought by a multinational and now manufactures in low labor cost Countries around the globe, same as Bosch.
For wire sets I think Kingsborne in SoCal is pretty good.
The old BERU management recommended them after I had sent them a letter (in German) a few years back.
Kingsborne used to use BERU ends, they now use Bremi.

 

For wire sets I think Kingsborne in SoCal is pretty good.

+1 They are...

Kingsborne Wire Werks Inc - Spark plug wires, Automotive, RV, Motorcycle, Marine, Racing, Industry

 

.

NGK does not recommend multi-ground electrode spark plugs for replacement where the original plug design did not call for them. This does not mean a multi-ground electrode plug would not work, but by application, NGK makes no recommendation.​

.

 

/\/\ Sounds like a statement to limit liability.

 

Could be. I'm no expert on plugs, just thought I'd share.

 

Thank you gentlemen :thumbsup: + :bowdown: Great info!

 

Concerns above
BERU Product finder | Federal-Mogul Global Aftermarket
If you do a Beru product search specific to a 420/500/560 W126 engine you will find Beru recommend Ultra Z62 / Ultra UX79 / Ultra X Titan UX2 / Ultra X Platin UX79P

The UX79 has a thick copper core coated with nickel and is a non resistor plug which i have been using for 3yrs now without fault and nothing but praise for them, so i fail to see all the negative hype.
Considering you can buy them for US$4.95 per plug i would not consider them expensive compared to a platinum plug around $10 each.

 

You can get them (UX79) a lot cheaper than that. I paid $2 per plug.

 

Just a re-fresher /update on this thread
My original Beru UX79 plugs that have been in the 5 litre coupe for a few years now are still going strong - engine does not miss a beat under any load/rev range
I swear by these plugs now after my own long term assessment over a 5 year period in which they have performed to perfection

Interested to get some feedback from other members who delved in and purchased a set of these UX79 plugs after i posted the info up on these plugs back 2yrs ago

 

Do these have 4 prongs at electrode? The ux79's that is?

 

Yes the UX79 4 prong and is a non resistor plug