The Mercedes-Benz 300E brake light requires a P21W bulb size for proper illumination and function. Data for the specified component covers the period from 1986 through 1993.
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 the P21W bulb across all brake light positions for the 1986-1993 model years.
The P21W is an ECE-standardized bulb, meaning it conforms to European and international automotive lighting regulations rather than SAE standards common in North American markets.
The P21W operates at 12 volts with a 21-watt output, which is a wattage typical of single-filament stop and signal applications.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
Because the P21W is single-filament, it serves only one lighting function per socket, distinguishing it from dual-filament bulbs such as the P21/5W, which handle two functions from a single housing.
The Mercedes-Benz 300E uses the same P21W specification for both the standard brake lights and the Center High Mount Stop Light across the full 1986-1993 production span, indicating a uniform bulb fitment across all brake-related positions.
The BA15s base is not interchangeable with the BA15d base, which carries two offset contacts. Substituting a BA15d bulb into a BA15s socket is not possible without modification.
P21W bulbs are widely available under multiple manufacturer part numbers, but fitment compatibility depends on the BA15s base type and the 21W rating rather than on brand designation alone.