The BMW 733i uses a 3893 bulb size for both front and rear side marker applications. The replacement chart covers 1978 to 1984 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 BMW 733i uses the 3893 bulb for both front and rear side markers across all model years from 1978-1984.
The 3893 is an ANSI-standardized bulb, meaning it conforms to a defined set of electrical and physical specifications recognized across the United States and Canada.
The 3893 operates on a 12-volt electrical system, consistent with standard automotive voltage.
As a dual-filament bulb, the 3893 contains two separate filaments within a single envelope, allowing it to serve more than one lighting function from a single socket.
The 3893 uses a BAY15d bayonet base, which is an offset twin-pin base. The offset pin placement prevents incorrect installation by ensuring the bulb can only be seated in one orientation.
The 3893 is classified as a specialty application bulb, indicating it is not among the most broadly distributed automotive bulb types and is intended for specific fitment contexts.
The same bulb size, 3893, is specified for both the front and rear side marker positions on the BMW 733i, meaning a single bulb type serves all four side marker sockets on the vehicle.
The consistent use of the 3893 across the entire 1978-1984 production run of the 733i indicates no mid-cycle change was made to the side marker bulb specification.