I know it's probably a stupid question but I was thinking about replacing the spark plugs on my 98 E-320. It requires 2 plugs per cylinder.
So what is the real advantage of having 2 of them? A resonance of spark?
Would both plugs be firing at the same time or just one? So that means they should last a very long time?

Not sure about the advantage but it's going to cost me quite a bit more:
12x8 = 96 vs
6x8 = 48 bucks.

Thanks in advance,
JeffreyP