The Mazda Cosmo front and rear side marker bulbs both utilize an 89 size bulb configuration. The replacement chart covers vehicle production spanning 1976 to 1978.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 89 bulb is the sole bulb type listed across all side marker positions on the Mazda Cosmo for the 1976-1978 model years.
The 89 is an ANSI-standardized bulb recognized in both the United States and Canada, operating at 12 volts and 13 watts.
It uses a BA15s bayonet base, which is a single-contact base with a 15mm collar and a single locating pin, designed to seat in one rotational position only.
The 89 is a single-filament bulb, meaning it serves one lighting function per socket rather than switching between two brightness levels.
The 89 is related to the more widely known 1156 bulb, sharing the same BA15s base type but rated at a lower wattage.
Because the 89 and 1156 share the same base, physical fitment in the socket is possible with either bulb, though the wattage difference means they are not electrically identical replacements.
The front and rear side marker positions on the Mazda Cosmo (1976-1978) share the same bulb specification, indicating socket compatibility between both locations.