Buick Super Back Up Light Bulb Size

The Buick Super back up light requires bulb size 1073 or P21W depending on the specific application. Data for the provided bulb sizes covers the range from 1954 to 1958.

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
1958	P21W
1954-1957	1073

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Lower wattage variant of 1156. 12V, 13W.	1073

Other Locations

Additional Notes

The Buick Super backup light specifications cover model years 1954-1958, with two distinct bulb types appearing across that span.
The 1073 is an ANSI-standard single-filament bulb operating at 12V and 13W, fitted with a BA15s bayonet base, and it serves the Buick Super from 1954-1957.
The BA15s bayonet base is a single-contact base, meaning the bulb seats and locks with a push-and-twist motion, with one contact pin on each side of the base at the same height.
The 1073 is a lower-wattage variant of the more common 1156 bulb, producing 13W compared to the 1156's 21W output, which affects brightness in backup light applications.
The 1958 Buick Super shifts to the P21W, an ECE-standard single-filament bulb rated at 12V and 21W, also using a BA15s bayonet base.
Although both the 1073 and P21W share the BA15s bayonet base, their wattage ratings differ significantly at 13W and 21W respectively, making them non-interchangeable without accounting for that electrical difference.
The P21W follows ECE regulations, a lighting standard used in Europe and internationally, which is a notable distinction from the ANSI standard governing the 1073.
Because both bulb types use the BA15s base, physical fitment into the socket is mechanically compatible, but the wattage difference between the two types means substituting one for the other affects the electrical load on the circuit.