The Saturn SC front turn signal requires a 2057 bulb size while the rear turn signal uses a P21W bulb size. The replacement chart covers vehicle production years 1991 to 1992 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 Saturn SC uses two distinct bulb standards across its front and rear turn signal positions, reflecting a split between North American and European lighting specifications on the same vehicle.
The 2057 bulb is an ANSI-standard type used in the United States and Canada. It operates on a dual-filament design with a BAY15d bayonet base, rated at 12V with filaments drawing 26.9W and 8W respectively.
The dual-filament configuration of the 2057 allows it to serve two brightness levels within a single housing, which is a common arrangement in North American automotive lighting where one filament handles turn signaling and the other handles a secondary function such as parking or running light duty.
The 2057 is described as a brighter variant of the 1157. While the two share the same BAY15d base and are physically interchangeable in many sockets, the 2057 draws more wattage on its high-intensity filament, making direct substitution a consideration when matching output levels.
The front turn signal position on the Saturn SC for model years 1991-1992 takes the 2057 bulb.
The P21W bulb is an ECE-standard type recognized across Europe and international markets. It is a single-filament signaling bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The BA15s base of the P21W is a single-contact bayonet fitting, which is physically incompatible with the dual-contact BAY15d base of the 2057. The two bulb types are not interchangeable despite sharing a similar bayonet-style mounting format.
The rear turn signal position on the Saturn SC for model years 1991-1992 takes the P21W bulb.