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Spark Plug Choices

I recently bought a used 2004 Mercedes SLK320 and I am doing the maintenance the used car dealer neglected. Mercedes owner’s manual recommends changing the plugs every 100K miles or 5 years. I only have 45K miles but the plugs are 7 years old. The Mercedes recommended plugs from Bosch cost about $6 each and the NGK long-life plugs about $12 each. Normally I wouldn’t quibble over the difference but this engine is a “twin-spark” so I need 12 of the little buggers.

Is there really any difference between brands of platinum plugs? If the car is only an occasional driver, I’ll likely hit the 5 years before the 100K miles so is the long-life feature a waste?

Thanks for the review of the SLK. Like you said, you only live once (especially if the airbags fail). I have lusted after an SLK for nearly nine years and I’m loving life right now.

I would use exactly the plugs specified by MB, and change them as the manual says. No real upside to non-stock plugs, in my opinion.

Put NGK in Japanese cars, AC in GM cars, Motorcraft in Ford cars and whatever Mercedes calls for in their cars. Assemble furniture using the instructions that come with it. Nothing wrong with being right. I build wooden weed wackers and if you saw one of them you would never stray from specifications. It’s scary, but Halloween is almost here too.

If the manual calls for Bosch, install the Bosch part number listed in the manual and replace at intervals called for in the manual. Installing something different will not gain you anything, and could in fact cause problems down the road, and for the love of God, avoid anything gimmicky, like those Pulstar plugs!