Oldsmobile Delta 88 Back Up Light Bulb Size

The Oldsmobile Delta 88 back up light utilizes unique bulb sizes 2057, 1156, and P21W depending on the specific production period. Available data covers the range from 1965 through 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
1965-1990	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 an ANSI-standard single-filament bulb operating at 12 volts and 21 watts, fitted with a BA15s bayonet base. It serves as the back up light bulb for the Oldsmobile Delta 88 across the 1965-1990 model years.
The 2057 bulb is an ANSI-standard dual-filament bulb operating at 12 volts with a high filament rating of 26.9 watts and a low filament rating of 8 watts. It uses a BAY15d bayonet base and is specified for the 1991 Delta 88.
The BA15s base of the 1156 and the BAY15d base of the 2057 are physically distinct bayonet fittings. The BA15s is a single-contact base, while the BAY15d is a dual-contact base with offset pins. These two base types are not interchangeable.
The 2057 is described as a brighter variant of the 1157 bulb. Although the 2057 and 1157 share the BAY15d base, their wattage ratings differ, which means substituting one for the other may affect light output.
The 1156 is a single-filament bulb, meaning it produces only one level of output. The 2057, by contrast, carries two filaments, supporting both a high-intensity and a low-intensity function within a single housing.
Both the 1156 and 2057 are classified under ANSI standards applicable in the United States and Canada, indicating conformance to a defined set of performance and dimensional criteria for the North American market.
The shift from the 1156 to the 2057 between the 1990 and 1991 model years represents a change in both filament count and base type for the Delta 88 back up light position.