Oldsmobile Cutlass Calais Back Up Light Bulb Size

The Oldsmobile Cutlass Calais back up light requires 2057, P21W, or 1156 bulb sizes depending on the specific version. Data for the bulb sizes covers the range from 1978 to 1991.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1991	2057
1988-1990	1156
1978-1984	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Brighter variant of 1157. 12V, 26.9W/8W.	2057
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156

Other Locations

Additional Notes

The 1156 bulb is the most frequently specified back up light bulb across the Oldsmobile Cutlass Calais lineup, appearing in model years 1978-1982, 1983-1984, and 1988-1990.
The 1156 is a single-filament bulb operating at 12V with a power draw of 21W, fitted with a BA15s bayonet base, and classified under the ANSI standard used in the United States and Canada.
The 2057 is specified for the 1991 Oldsmobile Cutlass Calais back up light, marking a departure from the 1156 used in prior model years.
The 2057 is a dual-filament bulb rated at 12V with filaments drawing 26.9W and 8W respectively, and it uses a BAY15d bayonet base under the same ANSI standard as the 1156.
The BA15s base of the 1156 and the BAY15d base of the 2057 are physically distinct, meaning these two bulbs are not interchangeable despite their similar bayonet-style mounting.
The BAY15d base features two offset pins, while the BA15s base has a single contact pin, a structural difference that prevents cross-fitting between the 1156 and 2057.
The 2057 is described as a brighter variant of the 1157, sharing the dual-filament design and BAY15d base with that bulb type, though the 1157 is not itself listed in these specifications.
Both the 1156 and 2057 conform to ANSI standards recognized in the United States and Canada, indicating standardized sizing and electrical ratings across both bulb types.