100,000 miles is long enough to change now... your fuel mileage suffers when
you don't change the plug. At today's gas price... it means everything for
that stupid spark plugs.
Generally speaking... copper plugs are good for about 30,000 miles...
whereas iridium plugs are like 100,000 miles. Use what MB specifies... do
not install platinum plugs. Everything else is somewhere in between.
I just looked up your spark plug. Original equipment shows 3 ground
electrodes... this is nice but alot of time, multiple electrodes makes
engine runs a bit rough... Alternate is single electrode... this can be use
without any problem at all. I'd probably pick the single electrode instead.