spark plug wires Bosch vs Beru
 

which is the better plug for a 420 sel, Bosch or Beru? why?

Either brand can be OE quality! BERU is always OE quality. IF you do opt for Bosch make sure to get "copper core" wires, Bosch also sells aftermarket quality that aren't copper-core!

Mercedes never used Bosch wires on 126 Chassis cars -- if they have ever used them period, it's a fairly recent development. They're better than they used to be, but that may not be saying much -- they used to be a complete joke. Stick with Beru -- they're good wires and they're OEM.

Virtually all modern spark plugs have a "copper core" - a central copper conductor. Common spark plugs have a nickel alloy electrode. "Premium" plugs usually have a platinum center electrode, which should last longer, especially if the plug is a "double platinum" type with a platinum button on the ground electrode. Mewer cars with double platinum plugs as OE usually have about a 60-100K recommended change interval.

The big difference in Mercedes-Benz spark plugs is that they are NON-RESISTOR type, so they are difficult to find in other than the OE supplied brands. Rather than using resistor type plugs to achieve EMI compliance, the spark plug boot has a metal shield that is grounded to the head.

There is some evidence that resistor type plugs exacerbate the tendency to rough idle and high emissions, so I always recommend sticking with the OE type non-resistor plugs, which considerably limits the field of readily available replacements.

I've never used Berus, but the Bosch Supers seem to have no problem with 30K miles of service and cost about two bucks each.

Duke

Hi Denis,

your heading mentions wires, your text plugs. From what I remember on this boards discussion, it's Beru wires (copper) and Bosch copper plugs, with the gap on the plugs widened a bit for better idle. Worked for my 420.
Reinhard Kreutzer

Yes, I didn't even know Beru made spark plugs, but the topic here is ignition wires, not spark plugs.

I'm not surprised -- I've just never seen them...

spark plug wires
 

my mistake, i meant to put plug wires in the body, not plugs, i had found some bosch plugs for $95, but if beru are the factor, i will search them out. anybody know of a place to get them at a decent price?