Spark Plugs: Resistor vs. Non-Resistor - PeachParts Mercedes-Benz Forum

cdplayer · #1 08-22-2007, 02:25 AM

Quote:

Originally Posted by MB-Dude

OK, I’m game. Whunter wrote a sticky entitled “Danger: RESISTOR SPARK PLUGS” in which the recommendation is to stay away from resistor spark plugs. Some discussion began and it was requested that further discussion continue in a new thread – so here we are. There has been a lot of emotion over whether resistor spark plugs are applicable to Mercedes, et. al. Opinion is sharply divided. This thread will explore people’s viewpoint.

I actually broached this question a couple years ago in another MB website and was ceremoniously crapped on. At the time, Bosch had just released their Platinium+4 product line:
http://jobs.boschusa.com/AutoParts/SparkPlugs/PlatinumPlus4/
…and I was interested in others views/opinions.

The ‘compelling’ argument against resistor plugs has always been one centered on this logic: MB Engineers chose Bosch non-resistor plugs… MB Engineers are smarter than us… so Bosch non-resistor plugs must be the *only* plug that will work, otherwise the MB Engineers would have chosen something different or given us options. There are other arguments, but this one seems to always boil to the surface.

This logic is unadulterated bull. Bosch non-resistor plugs are good quality plugs – no question – but they are also the least expensive for any auto manufacturer to use. The savings per automobile adds up pretty quick, as opposed to relatively more exotic, resistor plugs. MB Engineers do *not* engineer around a spark plug; they simply use a spark plug that is inexpensive to the manufacturing process. In other words, MB Engineers have other things to worry about than a simple US$0.50 (that’s 50-cents) per unit part bought in bulk through inter-company purchase agreements. My professional background as an Engineering Manager to a manufacturing company provides me a unique opportunity to understand the ‘drive’ of companies to save pennies in this manner.

I believe the use of Bosch non-resistor plugs is driven more by bottom-line profits than electrical engineering excellence. I welcome objective data that supports the claim that only non-resistor plugs are to be used in Mercedes motorcars. Folks claim to have read MB documentation that clearly indicates *only* non-resistor plugs are to be used. But as of this writing, no one seems able or willing to produce the objective information. Lots of theory… lots of ‘history’… lots of emotion… very little objective data.

I have run resistor plugs in various Mercedes over the years and seem to have had suffered no ill effects that can be attributed to resistor spark plugs. Performance differences have been, unfortunately, subjective. Thus, I do not profess to know one-way or another. But I am always interested in reviewing objective data. This thread is to address the question of whether resistor plugs (of any brand) can safely be used.

So, what do you think of the subject?

Just my two cents worth. I have a 1984 500SEC with now 265,000 miles on it. Car runs great. I have always used resistor plugs. No real reason other than I just thought they were better.

Now with this car and resistor plugs, I would notice carbon debris on the bumper when I was washing the car. Not much. But enought to turn the sponge a little black. I thought with the high miles, I was seeing evidence of blowby.

Then I read MB spark plug wires offer resistance in themselves. So by using resistor plugs, I was actually not getting a full burn on my fuel.

Made enough sense to me to replace my plugs with non resistor.
It's been about 4000 miles now and I have no more carbon deposits on the bumper. Same gas, same oil. Just no deposits.

For what it's worth...

MB-Dude · #2 08-22-2007, 04:41 AM

Quote:

Originally Posted by Hatterasguy

… The FSM is pretty specific about what you can use, I prefer not to backyard engineer things. …

Agreed, as a general rule. But MB owners seem to make claims about having technical data/information, but never seem to be able to produce it. I’m only trying to ferret out answers. I prefer to not blindly follow what MB Engineering states. Remember, these same "brain children" brought us the ML, et.al., mid-90's wiring harnesses, said Techron as a gas additive (any gas additive) is very bad, then changed direction 180º, etc., etc. I simply want to know "why" resistor plugs are not recommended.

The glory days of Mercedes-Benz are in the rear-view mirror. In my opinion, up until the early 90’s, perhaps a little earlier, MB engineering was awesome. After that, quality of engineering and manufacture went down the toilet. We cannot always use yesterday’s thinking with today’s MB vehicles.

Dpetryk – Your post poses a good question, but the original sticky represented the view that resistor plugs are bad. This thinking has been prevalent amongst MB owners for years. I’m not completely against the concept of non-resistor plugs use only, but struggle with not knowing why. And no one seems to be able to produce data (other than subjective personal experience or “the manual says so”). Inquiring minds want to know.

Quote:

Originally Posted by ASaltyDog

Say, can I use synthetic oil with resistor plugs?

Besides, real men don't need spark plug wires (et.al. 119/980)

Not sure. What does your MB Owner’s Manual say on the subject of synthetic oil use with resistor spark plugs? That's the standard response. Mine is vague on the subject.

Quote:

Originally Posted by JamesDean

this ***** is confusing. heres a question: why doesn't someone just ask mercedes? like their engineering team. heck I'm gonna email them and see what their official response is.

roar.

email sent to the Classic Center. We'll see what they say...

Of all the posts, this is the one I’m really watching out for. Yes, I could have e-mail’d the Classic Center myself, but I fear I would get a much generalized answer. Perhaps you might receive a better response. If I had contact information for MB Engineers directly, I wouldn’t be futzing around here with a no-win thread entitled Spark Plugs: Resistor vs. Non-Resistor. Regardless, I look forward to reading the reply from the Classic Center.

Quote:

Originally Posted by srjulianchivis

A simple question: I have installed Bosch platinum plugs #4020 in a 110 engine - there is no "R" in the number. (I could not care less about radio interference as all staions in the SF Bay Area now suck anyway). So are these plugs resistors or not?

Not sure. Here is the official Bosch Spark Plug Designation Guide… http://www.boschautoparts.com/NR/rdonlyres/C77B3446-232B-4AEC-AFA9-AD05F2A0A2AD/0/DesignationCodes.pdf
Sorry, can’t speak to the SF radio stations as I haven’t lived in the Bay Area for over 1-1/2 years.

Quote:

Originally Posted by cdplayer

… Then I read MB spark plug wires offer resistance in themselves. So by using resistor plugs, I was actually not getting a full burn on my fuel. …

Hmmm… Just out of curiosity, when was the last time the plug wires were changed? As a rule, as plug wires age they increase in resistance. I’m surprised the resistor plugs, by themselves, caused the small amount of soot.

280EZRider · #3 08-25-2007, 03:52 AM

Quote:

Originally Posted by MB-Dude

Agreed, as a general rule. But MB owners seem to make claims about having technical data/information, but never seem to be able to produce it. I’m only trying to ferret out answers. I prefer to not blindly follow what MB Engineering states. Remember, these same "brain children" brought us the ML, et.al., mid-90's wiring harnesses, said Techron as a gas additive (any gas additive) is very bad, then changed direction 180º, etc., etc. I simply want to know "why" resistor plugs are not recommended.

The glory days of Mercedes-Benz are in the rear-view mirror. In my opinion, up until the early 90’s, perhaps a little earlier, MB engineering was awesome. After that, quality of engineering and manufacture went down the toilet. We cannot always use yesterday’s thinking with today’s MB vehicles.

Dpetryk – Your post poses a good question, but the original sticky represented the view that resistor plugs are bad. This thinking has been prevalent amongst MB owners for years. I’m not completely against the concept of non-resistor plugs use only, but struggle with not knowing why. And no one seems to be able to produce data (other than subjective personal experience or “the manual says so”). Inquiring minds want to know.

Not sure. What does your MB Owner’s Manual say on the subject of synthetic oil use with resistor spark plugs? That's the standard response. Mine is vague on the subject.

Of all the posts, this is the one I’m really watching out for. Yes, I could have e-mail’d the Classic Center myself, but I fear I would get a much generalized answer. Perhaps you might receive a better response. If I had contact information for MB Engineers directly, I wouldn’t be futzing around here with a no-win thread entitled Spark Plugs: Resistor vs. Non-Resistor. Regardless, I look forward to reading the reply from the Classic Center.

Not sure. Here is the official Bosch Spark Plug Designation Guide… http://www.boschautoparts.com/NR/rdonlyres/C77B3446-232B-4AEC-AFA9-AD05F2A0A2AD/0/DesignationCodes.pdf
Sorry, can’t speak to the SF radio stations as I haven’t lived in the Bay Area for over 1-1/2 years.

Hmmm… Just out of curiosity, when was the last time the plug wires were changed? As a rule, as plug wires age they increase in resistance. I’m surprised the resistor plugs, by themselves, caused the small amount of soot.

I was once told by a very reputable mechanic at MBI Motors in Portland, OR that the original plug wires on my '77 280E were all copper and would probably last forever. The plug connectors - now that is a different story. After scoping my engine, he found two bad ones. I now have all new connectors with the original copper wires, 204,000 miles, recently changed plugs, and it runs great.

280EZRider · #4 08-25-2007, 03:26 PM

I just discovered that the Bosch Platinum plugs I recently installed in my 280E are in fact Resistors. I was also just told by the same parts guy who gave me this info that the OEM plug connectors have resistors in them as well. Today I'm purchasing new non-resistor plugs.