Oldsmobile F85 Back Up Light Bulb Size

The Oldsmobile F85 back up light utilizes the 1073 bulb size along with 1156 and P21W options for various lighting components. Data for the specific bulb requirements covers the range from 1961 through 1972.

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
1964-1972	1156
1963	1073
1961-1962	1156

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The Oldsmobile F85 uses the 1156 bulb for its back up light across the majority of its model years, specifically 1961-1962 and 1964-1972.
The 1156 is an ANSI-standardized single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base.
The BA15s bayonet base designation indicates a single-contact base with a 15mm barrel, a common format in automotive lighting applications of that era.
The 1963 Oldsmobile F85 is the sole model year in these specifications to use the 1073 bulb rather than the 1156.
The 1073 shares the same 12V operating voltage and BA15s bayonet base as the 1156 but draws only 13W, making it a lower-wattage variant of the same bulb family.
Because the 1073 and 1156 share the same base type, physical fitment is possible between the two, but the wattage difference means they are not direct electrical equivalents and substitution may affect output intensity.