Mercedes-Benz 300E front turn signal bulbs use P21/5W size while rear turn signal bulbs use P21W size. The replacement chart covers 1986 to 1993 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 300E uses two distinct turn signal bulb types across its front and rear positions, with the front requiring P21/5W and the rear requiring P21W for all model years from 1986-1993.
The P21/5W is a dual-filament bulb, meaning it carries two separate filaments within a single envelope, rated at 21W and 5W respectively, operating on a 12V system.
The P21W is a single-filament bulb rated at 21W on a 12V system, dedicated solely to the rear turn signal function on the 300E across all listed model years.
The P21/5W uses a BAY15d bayonet base, while the P21W uses a BA15s bayonet base. These two base types are not interchangeable, as the pin offsets and filament configurations differ between them.
Both bulb types conform to ECE standards, a regulatory framework recognized across Europe and numerous other markets worldwide, which governs output, base configuration, and labeling.
The dual-filament design of the P21/5W in the front position suggests the bulb serves more than one lighting function simultaneously, with the lower 5W filament typically associated with a secondary role such as a parking or position light.
The front turn signal position on the 300E specifies the P21/5W across the full 1986-1993 production span without variation, indicating a consistent lamp housing design throughout the model's production run.
Substituting a P21W for a P21/5W in the front position would result in an incorrect base fit, as the BAY15d base of the P21/5W has offset pins designed to prevent incorrect installation of single-filament bulbs.