The Lexus GS350 back up light requires a bulb size of 921 for the specified automotive lighting component. Available data for the bulb size covers the range from 2007 through 2015.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 921 bulb is an ANSI-standard wedge type in the T15 form factor, rated at 12 volts and 16 watts, and it serves as the back up light bulb across the Lexus GS350 model years 2007-2015 in the standard position.
The 3057 bulb is an ANSI-standard dual-filament wedge type in the T25 form factor, rated at 12 volts with a dual-wattage output of 27W and 7W corresponding to its two filaments.
The inner back up light position on the Lexus GS350 uses different bulb sizes depending on the model year, which means the two sub-groups within this position are not interchangeable with one another.
For the 2013-2015 GS350, the inner back up light requires the 3057 bulb, while the standard back up light position retains the 921 for those same years.
For the 2007-2011 GS350, both the standard and inner back up light positions use the 921 bulb, making the fitment uniform across both positions during that period.
The 921 and 3057 bulbs share the same 12-volt operating voltage, but they differ in wattage and filament count, making them electrically and physically distinct and not substitutable for one another.
The T15 and T25 designations refer to the tubular wedge base sizing of each bulb, with T25 being the larger of the two, which is a factor in physical fitment within the socket.
The dual-filament nature of the 3057 means it carries two independent circuits within a single bulb, a characteristic that distinguishes it from the single-filament 921 used elsewhere in the same vehicle.