Spark plug replacement
 

Am about to get a used ML 350 in the near future. I have been told that the spark plugs must be "timed". Not sure what this means or if it is a valid claim. I have never heard of anything like this before. Was told if not timed correctly it would over time burn a hole in one of the valves. Was told to only use Mercedes branded spark plugs. Can anyone confirm this? Thanks!

They are probably talking about "indexing" vs. "timing" of the spark plug. Indexing puts the rotation/clock position of the grounding electrode aiming at a specific point. I've read sans personal experience that some of the factory plug installations are indexed. Would be best to find the factory plug replacement method to follow.