I would like to get an opinion and some help. I have a 1992 300-E M103-983 six cylinder . The car has 37239 miles only. When is the approprate time to change the spark plugs? I got the Bosch super H9 DCO 0 241 225 573 spark plugs from flast lane. The engine is not missing or having any starting problems.
Should I wait to a certain milage before replacing the plugs.

What is the gap these plugs should be set at? I have the Hazet puller so not to damage the spark plug wire ends and the factory spark plug tool to remove the plugs. Also what tork is approprate to seat the plug cold when doing the service. I cannot fine this information in my engine factory manual.

Thank You
Bob Geco