Chevrolet S10 Back Up Light Bulb Size

Additional Notes

• The Chevrolet S10 uses two distinct back up light bulb types across its model years: the 3057 and the 1156, both of which conform to ANSI standards recognized in the United States and Canada.
• The 1156 bulb is a single-filament type with a BA15s bayonet base, rated at 12V and 21W. The BA15s designation indicates a single-contact bayonet cap with a 15mm base width.
• The 3057 is a dual-filament wedge bulb in the T25 form factor, rated at 12V with a 27W high filament and a 7W low filament. In back up light applications, only one of the two filaments is typically active.
• The 1156 bulb appears in the Chevrolet S10 from 1982-1993, making it the fitment associated with the earlier production span covered by these specifications.
• The 3057 bulb is specified for the 1994-1996, 1998, and 2004 model years of the S10.
• Because the 1156 is a single-filament bayonet-base bulb and the 3057 is a dual-filament wedge bulb, the two types are not interchangeable. They differ in both base design and filament configuration.
• The transition from the 1156 to the 3057 occurred between the 1993 and 1994 model years of the S10, reflecting a change in socket and bulb format.
• The BA15s bayonet base of the 1156 uses a twist-and-lock installation method, while the T25 wedge base of the 3057 is held in place by friction within its socket, requiring no rotation during installation.