The Kia Optima brake light components utilize 1157, 2357, and P21/5W bulb sizes depending on the specific version of the vehicle. Data for the provided specifications covers the range from 2001 to 2020.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1157 and 2357 are the two brake bulb types used across the Kia Optima's model years, and both follow the ANSI standard applicable to the US and Canadian markets. Each uses a BAY15d bayonet base and operates at 12V, making them physically interchangeable in terms of base fitment.
Although the 1157 and 2357 share the same BAY15d bayonet base, their wattage ratings differ. The 1157 draws 21W on its high filament and 5W on its low filament, while the 2357 draws 26.9W and 8W respectively, making the 2357 the higher-output variant of the two.
The Kia Optima uses the 1157 brake bulb for 2011-2013 and 2017-2020, with the 2017-2018 entries specifying Single Projector-Type Headlamps and the 2011-2013 and 2019-2020 entries specifying Halogen Capsule Headlamps as the qualifying condition.
The headlamp type listed alongside the 1157 specification indicates that brake bulb fitment on the Kia Optima is tied to the vehicle's headlamp configuration, meaning two trim variants within the same model year may require different brake bulbs.
The 2357 brake bulb applies to the Kia Optima for 2003-2010, with no headlamp condition qualifier attached to any of those entries, suggesting a single fitment applied across all trims in those years.
The 2001-2002 Kia Optima uses the 1157 for the brake light, while the center high mount stop light for those same years uses the P21W, an ECE-standard single-filament bulb with a BA15s bayonet base rated at 12V and 21W.
The P21W differs from the 1157 in both standard and base type. The P21W follows the ECE standard and uses a BA15s single-contact base, whereas the 1157 follows the ANSI standard and uses a BAY15d dual-contact base, making the two non-interchangeable despite similar wattage on the high filament.
The center high mount stop light for the Kia Optima uses the 921 bulb for 2003-2010. The 921 is a wedge-type bulb in the T15 form factor, rated at 12V and 16W, and follows the ANSI standard.
The 921 wedge base and the BAY15d bayonet base used by the 1157 and 2357 are physically incompatible, meaning the center high mount stop light socket and the standard brake light socket on the Optima are not designed to accept the same bulb.