In my attempts to read spark plugs I stumbled across the following Forum article which seems quite easy reading and well illustrated:
https://www.bimmerforums.com/forum/showthread.php?1282968-Ultimate-Spark-Plug-Reading-Thread
Perhaps this may benefit some??
https://www.bimmerforums.com/forum/showthread.php?1282968-Ultimate-Spark-Plug-Reading-Thread
Perhaps this may benefit some??