The Mercedes-Benz ML55 AMG front fog light uses H8 and H3 bulb sizes, while the rear fog light requires a P21/4W bulb size. The replacement chart covers 2000 to 2003 model production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz ML55 AMG front fog light specification changed from H3 in 2000-2001 to H8 in 2002-2003, making these two bulb types non-interchangeable across those model years despite both serving the same fog light function.
The H3 bulb operates at 12V and 55W, drawing notably more wattage than the H8, which operates at 12V and 35W. Substituting one for the other without confirming the correct year fitment risks a mismatch in both wattage and base type.
The H3 uses a PK22s base, while the H8 uses a PGJ19-1 base. These bases are physically incompatible, so a bulb intended for one generation of the ML55 AMG front fog housing will not physically seat in the other.
Both the H3 and H8 are single-filament halogen bulbs built to the ECE standard, which governs lighting equipment across Europe and much of the world. Both also carry approval for use in the United States, and the H3 additionally holds approval in Japan.
The rear fog light specification for the ML55 AMG is consistent across all four model years from 2000-2003, with the P21/4W bulb used throughout.
The P21/4W is a dual-filament bulb rated at 12V with a 21W main filament and a 4W secondary filament. It uses a BAZ15d bayonet base, which is an offset-pin design that prevents incorrect installation of single-filament alternatives.
The BAZ15d base on the P21/4W is distinct from the more common BA15s and BA15d bayonet bases. The offset pin spacing is specific to dual-filament bulbs with unequal wattage ratings, reinforcing that a standard single-filament P21W would not be a direct physical substitute.
The P21/4W carries ECE certification, placing it within the same international regulatory framework as the H3 and H8 halogen bulbs specified for the front fog positions on the same vehicle.