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#1 · Apr 3, 2008 (Edited) Are these the correct plugs for the '84 500SEL? I have never heard of these, but they are installed int he car. What spark plugs would you recommend for that engine? Again, the installed plugs are Bosch W9DC. Other numbers on the plug are Super RO 390. The measured gap is about 0.042, but should be 0.032 on a new plug and these look pretty new to me. Sort by Oldest first Oldest first Newest first Most reactions #2 · Apr 3, 2008 Please complete your profile with a location (or at least a Country) by clicking 'User CP' on the top tool bar, it makes it easier for members to offer advice. Mercedes Benz made Country specific versions of our cars. The W-DC, and W-DCO non resistor plugs are no longer made by Bosch. Anything with an 'R' like in WR means resistor plug, not really good for our cars, neither are the Platinum etc. I once spent quite a bit on Bosch Plarinum +4, only to throw them out after one week. The W-DCO was specifically made for the Mercedes V-8 and has a larger core electrode (see the Bosch website). The W9DC was a slightly cooler burning plug for cars in hot climates. In a cooler climate you might use an 8, in a cold climate a 7. The NGK BP7ES is compatible with the Bosch W9DC and works well in our V-8's. Even though it's not in your profile, the W9DC means you live in a warm climate. In Germany I would look for BERU spark plugs. The experts recommend a bit larger gap than .032, .042 is good. A forum search with 'Spark Plug Gap' will get you a better idea. Cheers

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#3 · Apr 3, 2008 Resistor plugs & supressors.

Teutone said: The W-DC, and W-DCO non resistor plugs are no longer made by Bosch. Anything with an 'R' like in WR means resistor plug, not really good for our cars, neither are the Platinum etc. Click to expand...

Hi Teutone, Something i've searched for but found no responses for: Since our cars use non resistor plugs + 1KOhm suppressors, wouldn't also be OK to use resistor plugs if we use supressorless cables, proven that the final resistance is similar to 1K? Greetings, Flavio. Show more replies 0 Reply #5 · Apr 3, 2008 The NGK BP7ES plugs are pretty hard to find in FL-- had to get mine from West Marine --(they only had 6 in the werehouse)-- had to order the remaining 4 autozone had at their werehouse---- weired anyone else running short on these?? #7 · Apr 3, 2008 I usually find them here at Pep Boy's. But each branch carries only 4-6. Cheers 0 Reply #6 · Apr 3, 2008 I have heard that Bosch is no longer manufacturing the "SUPER" copper plugs anymore (yellow,red and green on the box) that is all I have used for years! I have avoided the platinum +4 hype.. W9DCO is a great plug.. #8 · Apr 3, 2008 Get friendly with your local Mercedes Benz dealership parts counter personnel. At my dealer, I have several times given all the guys there anything from 4 watt tactical lights, to 1 watt mini flash lights and other items we import. Now, the guys are kind enough, to usually give me 30% off my parts buys. The dealer often has cases of the W-DCO in stock, and hoards them. They are likely to be inventoried under a different computer code / part # known to the parts manager, and won't show up with a regular search. Cheers 0 Reply #9 · Apr 4, 2008 I have a small stash of the Bosch W8DC's for sale if you need them! - Steve #10 · Apr 4, 2008 These are the plugs that sparkplugs.com lists for '84 500SEL: Sparkplugs.com - Application Search Results I do not believe all these would perform well in that engine. Which ones would you recommend on that list? Are platinum plugs OK to use? #11 · Apr 4, 2008 Thanks for completing your profile. The list has Irridium, Platinum, and a bunch of others with an 'R' , meaning resistor. Not what you really want. Ask your friendly MB dealership parts counter guy to go into their stash of Bosch W9DCO, (for your climate), otherwise go for NGK BP7ES at parts stores, and gap either plug wider than spec. .042 (our resident MB experts advice), and all will be well. Cheers 0 Reply #12 · Apr 17, 2008 Difference between BOSCH Wx-DC & Wx-DCO What's the difference between BOSCH W7DC & W7DCO? Are they interchangeable? The W7DCO is what my manual calls for my Euro 560SEL. After searching ebay, I find it is indeed very hard to find remaining stock of W7DCO, but W7DC is much more common as it is the also the plug used by VW, Rover, and Austin. #13 · Apr 17, 2008

mkyang said: What's the difference between BOSCH W7DC & W7DCO? Are they interchangeable? The W7DCO is what my manual calls for my Euro 560SEL. After searching ebay, I find it is indeed very hard to find remaining stock of W7DCO, but W7DC is much more common as it is the also the plug used by VW, Rover, and Austin. Click to expand...

As far as I know, both W-DC, or DCO are the right plugs for the V-8, but the DCO was made by Bosch especially for the MB V-8 (check the Bosch website, it explains it). Cheers Edit: The DCO has a larger center electrode. 0 Reply #14 · Apr 17, 2008 The guy at marine west said... "Hey sonny, some guy came in here to buy these after his boat started to run like crap, i told him not to put in those crappy automotive resistor plugs"....then he said....."so what kind of Boat do you have?" .... I almost tried not to laugh at him when I told him what kind of BOAT it was going into!!! ----The M117 would make a nice featherweight motor for a ciggarette boat i guess! This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread. Insert Quotes Post Reply

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