I just changed the spark plugs in one of my 2003 C230K (we got two in the family), and when I pulled the original plugs they didn't match the ones I bought. Not even close! I got NGK LFR6A-11, the non-iridium version of what the car was supposed to have. The car had Autolite APP 3924 double plat. installed, which belong to the C320 from what I've been told. If they were close to each other I wouldn't mind so much, but there's a difference in thread depth that's huge. The NGK and the Bosch plat. (which were installed in my other C230K) have 26.5 mm of threads from base to tip, and the Autolites are 18 mm long. I've owned the car from new and never had the plugs changed or touched during service, so did the factory install the wrong plugs? Has anyone else seen anything like this in their car? Since I changed them, the car has more power, runs smoother, and gets 4-5 mpg more than before. If you've seen anything like this before please let me know.

jasonS
2003 C230 kompressor sport (x2)

 

Interesting, I doubt that they came from the factory like that. I can guess the car was at the dealer, perhaps even before you bought it, and someone replaced the plugs on the wrong car. I don't see Autolite suggested in the service specs at all.