For 99.9 % of the 300E out there the F9DC0 plug is the best bet for the $$$. By opening the gap, the engine will have a better idle. Most electronic ignition systems like a wider gap & at dealer we set plugs at 1mm(.039"). Platinum plugs are for 1998 & later cars. The OE plugs are copper core & will last as long as the platinums on your car.