OT,kinda. Interesting thing on a mercedes e320 i was working on yesterday.

[Bill R.]

It has 3 coils , one over each of 3 sparkplugs, then it has a plug wire from the side of these coils going to another cylinder,so each coil fires 2 cylinders just like a lot of cars.. the interesting thing is that the spark plugs that have the coil sitting on top of them wore from the center electode and rounded it off and away. The plugs that had the wire going to them wore from the top electrode. This was consistent on all of them.

[Bill R.]

obvious as this e320 was .... but all the gm cars that use a coil to fire 2 cylinders with the wasted spark method do this..

[632 Regal]

wierd stuff there!

[bahnstormer]

n3wbs.... =\

[Jon K]

Mercedes has been doing this other really weird thing too... I think their box of clutch pedals got infection or something, they haven't been putting them in cars.

[TheDuke]

SLK320 has a 6 spd manual and C series comes with a 5 or 6 speed tranny. But except for that I haven't seen anything else from uncle Benz with a stick since early 90's.

[gale]

Makes sense to me, the one closest to the coil is going to have a higher voltage delivered to it vs. the higher inductance and resistance losses on the one fed by the wire & the closer one will ablate away more metal at a faster rate. I'm surprised the Mercedes engineers designed them like this and didn't mount the coil mid-way between the plugs and feed them both with equal length wires. Looks like the plugs had a few too many miles on them and probably had some idle/emissions issues?

[Bill R.]

one plug wears only on the center electrode and the other wears on the side electrode, the direction of current flow is different on them... The multi coil gm cars have plugs wires on all of them and they still do this. Actually these plugs were changed just about when they specified with these long life intervals on them , no emissions problems , she just wanted the routine mileage maintenance done. In fact she didn't know that the plugs were required at this time, along with a bunch of other stuff.

Makes sense to me, the one closest to the coil is going to have a higher voltage delivered to it vs. the higher inductance and resistance losses on the one fed by the wire & the closer one will ablate away more metal at a faster rate. I'm surprised the Mercedes engineers designed them like this and didn't mount the coil mid-way between the plugs and feed them both with equal length wires. Looks like the plugs had a few too many miles on them and probably had some idle/emissions issues?

[Interceptor]

SLK320 has a 6 spd manual and C series comes with a 5 or 6 speed tranny. But except for that I haven't seen anything else from uncle Benz with a stick since early 90's.

That's because you live in the US. Here in Croatia (Europe) nearly 90% of the MB cars are manual. This goes for other cars, too.