Oldsmobile Omega Back Up Light Bulb Size

The Oldsmobile Omega back up light requires bulb sizes 1156, 1157, or P21W depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 1973 to 1984.

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
1980-1984	1156
1979	1157
1973-1978	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157

Other Locations

Additional Notes

The Oldsmobile Omega uses the 1156 bulb as its back up light across the majority of its model years, specifically 1973-1978 and 1980-1984.
The 1156 is an ANSI-standardized bulb recognized in both the United States and Canada, operating at 12 volts with a 21-watt output and a single filament design.
Its base type is the BA15s bayonet mount, a single-contact configuration in which the bulb locks into the socket with a twist.
The 1979 Oldsmobile Omega back up light takes the 1157 bulb rather than the 1156 used in surrounding model years.
The 1157 is also an ANSI-standardized 12-volt bulb, but it carries a dual-filament design rated at 21W and 5W, serving two separate electrical circuits within a single housing.
The 1157 uses a BAY15d bayonet base, a dual-contact mount that is physically distinct from the BA15s base of the 1156, making the two bulbs non-interchangeable despite their similar appearance.
Because the 1156 and 1157 share a 12-volt operating voltage and an identical 21-watt primary filament rating, they are sometimes mistaken for equivalent parts, though their base configurations prevent direct substitution.