I owned my 1999, C280 sport for several years and the Champion spark plugs were very good plugs and made the engine run smooth and strong. I also have recently put the Denso Iridium spark plugs in and those plugs are at most slightly to no better than the Champion plugs.

The Champion plug part number is 7071/RC12PYP.

While the OEM stuff is good there are other products as good and in some cases better than OEM and less costly to boot.

Jeff