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'89 420SEL, '93 300E and '07 Hyu Santa Fe
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562 Posts
Discussion Starter #1
So i have decided to change all spark plugs on both my 300E and 420sel as i don't remember when it was last changed.

I searched forum and got following suggestions.

300e - bp6efs or t20ep-u or w8dc
420sel - bp6es or bp7es

Question is - Is there a spark plug that is common on both cars.
I hope bp7es can be used as it's selling for 0.83 :D at amazon and with oil and air filters i will get free shipping.
 

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Registered
'89 420SEL, '93 300E and '07 Hyu Santa Fe
Joined
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562 Posts
Discussion Starter #2
Great.
After posting this it's sold out now.
Congrats to who got it but at least someone can answer for me here I will get it accordingly.
Btw Happy thanksgiving everyone.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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40,653 Posts
Great.
After posting this it's sold out now.
Congrats to who got it but at least someone can answer for me here I will get it accordingly.
Btw Happy thanksgiving everyone.
The NLA bosch H9DCO for the M103 6 banger, and W9DCO for the M117 * cyl was a non resistor plug, with DCO denoting a large center electrode for our engines. Anything with an R is a resistor plug. Bosch made these also in DC. None of these bosch have been made in 10+ years or so, but quantities do show up sometimes.
A cooler running 9 would be suitable for CA hot climate, a 7 on the east coast, and even 6 in cold parts of CA for example.
Bosch now only sells a WR.... = resistor. Avoid anything platinum, irridium etc, our engines don't seem to like them. Pep boys carries the non resistor BP7ES (or 6 etc) recommended gap 42 or 44. Usually their stores carry only 4, and you may have to buy from 2 stores.
The reason for non resistor plugs, our ignition wire sets have resistors build into the spark plug booth.

The old Bosch DC was also suitable.
For more in depth info search the forum with 2 keywords http://www.benzworld.org/forums/w126-s-se-sec-sel-sd/announcement-new-members-welcome-please-read.html
 
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