Best available spark plugs for 1966 230SL

[Ed Riefstahl]

Greetings,

After reading and re-reading the thread from April regarding best spark plugs, I am still uncertain with regards to available substitute plugs. If I'm not mistaking, I believe non-resistor plugs would be the best if possible.

I am currently running a set of aging Bosch WR9DC and would like a new set before our road trip to Canyon Lands in July. Benz Dr said in the last thread, he ran W9DC and NGK BP5ES, however both are no longer available.

In doing quite a bit of searching for plugs, even on MB parts sites, by accident I discovered Amazon offers both NGK BP5ES and BP6ES, along with resistor version.

Would anyone like to make a recommendation? The NGK appear to be the real deal. However these days often times you're just buying a name.
Any reason not to buy the NGK from Amazon and should I go with the BP5ES or BP6ES? If there is a better available plug, by all means I'd like to know. I do have the option of cleaning and gaping my existing plugs. They have been in the car for at least 10 years, and show only minimal electrode loss. I was thinking a non-resistor might be a better choice.

Thanks in advance for any suggestions or comments.

Ed Riefstahl
Erie, PA
1966 230SL (Ms Magoo) Horizon Blue
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5


 

[Mike Hughes]

NGK plugs have worked well for me over many years in multiple makes of cars.  If you can find BP5ES, get them.

[Cees Klumper]

What I did, I got two sets of each 5, 6 and I think even 7 of the NGK BPxES so I can experiment and see what heat range my engine runs best on. Not sure what I am running currently as I am still in California and the car is in France, but we'll be reunited for the summer as from June 30 so I can check then ...
You can just make out the NGK boxes on the left in the photo.

[Vander]

I would bet that if you buy BP5ES on Amazon, you will actually receive BP5RES

Which you don't want. The problem is NGK tells parts distributors that BP5RES supercedes BP5ES, so they sell it to us not knowing it is bad and completely different for our application.

[Ed Riefstahl]

Hello Vander,

This is one of the reasons for my posting the questions. I spent considerable time on this before posting. You are absolutely correct, many of the BP5ES are listed as such, but when you click on "product information" you find that they left the R out in the listing, but they are actually resistor plugs.

I have however found some that are stamped on the metal and printed on the porcelain BP5ES. It also lists as such in the product information. Also lists manufacturer as NGK. Not so with the resistor plugs, when reading the product information, the manufacturer is listed as Stens. If you look further, often you can see the part number has "R" in it.

I think I will order them and let you folks know how I make out. I wish there was a way to visually tell the difference.

Have a great weekend!
Ed Riefstahl
Erie, PA

1966 230SL (Ms Magoo) Horizon Blue
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5

[Mike Hughes]

Search for "NGK 7832" to find BP5ES plugs with the removable screw caps.

[Cees Klumper]

The non-resistor ones I have, 5, 6 and 7 NGK series, I believe I bought on Amazon in Europe, and they are all the correct non-resistor ones and, as of a few years ago, not expensive and easy to find.

[Ed Riefstahl]

Well, Vander won the bet. Amazon sent me BPR5ES. The packing list states BP5ES. The ad including all photos of the spark plug and the box show BPR5ES. Even reading the "additional product information" fine print below, it lists the plugs as non-resistor. I'm not sure if they're trying to pull a fast one on us or what. I'm pretty discouraged, you might say.

I also did a search for NGK 7832, as Mike Hughes suggested, however when I read the fine print it's a resister plug. Mike, if you have a source, I'd sure appreciate you passing it along.

At this point, I don't have any other option. I received my new cap and rotor. I also have the solid copper wires on their way. I'd really like to replace my aging Bosch WR9DC with non-resistor plugs, but I guess I'll clean and gap them and put them back in the car. I'm not sure I'm really gaining anything by putting in a new set of resistor plugs. I've spent a great deal of time searching for these and it's time to move on.

We are still planning our cross country trip to Utah in our Pagoda around the 4th week of July. I sure was hoping for a complete tuneup, including plugs, before we leave.

Any suggestions are greatly appreciated.

Ed Riefstahl
Erie, PA

1966 230SL (Ms Magoo) Horizon Blue
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5

[BobH]

Hello Ed, that's really strange, BP5ES are plentiful in the UK and probably Europe, can't see why they're scarce in the US

Authentic Classics seem to have a selection of Bosch non resistor plugs, i've read either W9DC or W7DC are suitable, perhaps search on here or on a comparison site to see which is closest to the BP5ES plugs, although it looks like the 9's are out of stock at the moment

https://www.authenticclassics.com/230SL-250SL-280SL-Convertible-113-Chassis-s/1.htm?searching=Y&sort=7&search=spark+plugs&show=36&page=1

Just checked the Tech Manual seems the W7DC was the recommended plug for our cars, not sure why this has now changed to the NGK, perhaps the Bosch were also unavailable at one time?  If you want a slightly hotter plug and the 9's aren't in stock, perhaps try an 8

[Raymond]

Here in the states, I found the non-resistor BP5ES from a motorcycle supply shop.

[mdsalemi]

There were two issues with the NGK plugs. First the scarcity of the non-resistor version, then newer ones didn’t have the screw off top. Luckily I was able to get a lifetime supply

[mBdrvr]

Raymond: Which motorcycle shop?

[BlackForest]

The Bosch W7DC non-resistor plug is still available from the dealer at a list price of $7.75 ea.
Part number 003 159 12 03

Michael

[CFF]

You can buy the proper none resistor Bosch plugs from the Mercedes classic center. They are the only authorized seller of them.

[Ed Riefstahl]

Thanks guys,

I ordered a set of W7DC from Authentic Classics. They arrived today. I was hoping for W9DC. Authentic lists them, but no longer available.

As it turns out, my Bosch wires are solid copper core and in perfect condition, so I will use them. For whatever reason, the coil wire was carbon center. So, I replaced it with a solid core, along with a new cap & rotor.

For those of you that don't follow the General Discussion, i do have a thread started and looking for travel information for the Pagoda road-trip to Canyon Lands on secondary roads. We will be taking the trip later in July. We would love to hear of some cool, less known places between here and there.

Ed Riefstahl
Erie, PA

1966 230SL (Ms Magoo) Horizon Blue
1970 280S (Miss Daisy)
1999 BMW Z3 5 speed
1991 BMW 318I 5 Speed
1997 Toyota Paseo Convertible - One of 1000, (have you ever seen one?)
1997 Ford Ranger step side (Mater)
2023 Mazda CX 5