Bought a new spark plug for the c400GT
- Thread starter nbevan
- Start date
wspollack
Active member
1) It's been my experience (from reading, actually replacing, etc., over the years) that in modern times you do not need to mess with the gap in spark plugs, in ordinary motor vehicle applications.
That is, half a century or so ago, yes, you often had to adjust the gap of the more general-purpose spark plugs. These days -- I'm talking the last couple of decades -- you are often specifically warned by the manufacturers of the engines and by the manufacturers of the spark plugs themselves NOT to alter or otherwise mess with the electrodes. That is, by and large these days, the factory gap is the correct one, and altering the plug in any way is likely to damage it.
2) The plug used for the C 400, according to my version of the shop manual, is the NGK LMAR8J-9E
3) Here's one more page, but that's it:
4) It seems to me that if you have to ask some basic questions about accessing the plug, you might be better off letting a BMW dealer or an independent shop do the work for you. I don't mean to insult you or your ability here -- I will be letting the dealer do this sort of work for me, too -- but I wonder whether this is some task best left for a profession (in our particular cases -- I'm sure many forum members can do this work themselves.
5) You might inform us, just out of curiosity and shared knowledge, what prompted you to purchase a new plug.
wspollack
Active member
FWIW, the owner's manual says to replace the spark plug at 12,000-mile intervals.