I've got a 98 E320 that I've had about 5 years. Recently I've noticed the fuel economy is much lower than it used to be. I know it's not the air filter, because I changed it last year. I started looking through the records, and the best I can tell, it has the original spark plugs (145k miles). I pulled one, and sure enough, it looks pretty bad.

I went to buy replacement plugs, and like all vehicles, there were a slew to choose from. I intend to stick with Bosch, and the parts finder here lists the FR8DPP33 and FR8DPP33+, apparently the Super and Super Plus.

On the other hand, the parts store I went to shows the Bosch 4418 and 4301, apparently the Platinum 4+ and Platinum 2+. These are the ones with 2 or 4 ground electrodes that sort of make an arch over the center electrode.

Does anyone have any experience with these? The Bosch website seems to imply they are better.