which spart plugs
 

in my 1990 300 SEL which spark plugs should I get ( the last set I cannot remember when I had them put in) and are they hard to do? My mechanic just retired and I am between mechanics (I will not take it to a dealer) My 1991 560 I won't even attempt as well as my wife's ML until I find a good MB mechanic

Well, you could just pull a plug and see what's in there assumming your happy now. The plug installed at the factory is listed in the back of the owners manual but after 19 years it may have been replaced by a newer number. Most MB OEM plugs are Bosch so you can also go to the Bosch site (google) and input your car/model/year and see what's recommended. Some people prefer the single electrode plug. Generally the recommendations start with the multi-electrode so scroll down to find the single electrode plug rec if that matters to you. Good luck.

M103 spark plugs are a huge debate. As for me, I run what I've found to work best. Which at the moment are some junky champion plugs! :eek:

The true Bosch "correct" plug for that engine as per the dealer is the H9DCO set to a gap of .032 to .034 (they usually come pre-gapped at .032 which is fine)

Yeah, lots of posts on this exact subject. Do a search. I recently used the Bosch plugs on sale here at Fastlane, the Copper + Yttrium variety, and so far they seem to be working quite well. I assume they're the non-resistor variety, since that seems to be the consensus on which type to use. I hope I'm correct in that assumption.....

-tp

Nope, the ones on fastlane are Resistor plugs. However, I've been running resistor plugs in my 300E, and it runs a lot better on them than it did on some non-resistor Bosch's I got from the dealer....weird....they got all fouled up real fast. But the Resistor champions I have in there result in smooth running, good power, and don't foul up. Explain that! :D