Oldsmobile Jetstar I Back Up Light Bulb Size

The Oldsmobile Jetstar I back up light requires bulb size 1156 or P21W depending on the specific application. Data for the bulb sizes covers the range from 1964 to 1965.

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
1964-1965	1156

Bulb Specifications

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

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Additional Notes

The 1156 is the specified back up light bulb for the Oldsmobile Jetstar I across both available model years, 1964-1965.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical characteristics conform to a defined North American specification recognized in both the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive incandescent back up light applications of that era.
The bulb uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant with which it is not interchangeable.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that combine two functions such as stop and tail within one housing.