Kia Optima Turn Signal Bulb Size

Additional Notes

• The 2357NA bulb is the most frequently specified front turn signal bulb across the Kia Optima model range, appearing in 2001-2008, 2011-2013, and 2018-2020. It is a dual-filament, 12V bulb rated at 26.9W on its high filament and 8W on its low filament, fitted with a BAY15d bayonet base and natural amber glass.
• The natural amber glass coating on the 2357NA and 1156NA variants produces the amber signal color directly from the bulb itself, rather than relying on a colored lens housing to filter a clear bulb.
• The 2357 bulb, specified for the front turn signal on the 2009-2010 Optima and for several earlier model years, shares the same BAY15d base and 26.9W/8W dual-filament configuration as the 2357NA but lacks the natural amber glass coating.
• The 1156NA is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W. It serves as the front turn signal bulb on the 2017 Optima and as the rear turn signal bulb on the 2019-2020 Optima, among other years.
• The BAY15d base used by the 2357 and 2357NA is a dual-contact bayonet fitting, while the BA15s base used by the 1156 and 1156NA is a single-contact bayonet fitting. These two base types are not interchangeable.
• The 2017-2018 Kia Optima rear turn signal position requires two different bulbs depending on trim configuration. Vehicles with LED tail lights use the 1156, while vehicles without LED tail lights use the PY21W.
• The PY21W follows the ECE standard rather than the ANSI standard used by all other bulbs in these specifications. It uses a BAU15s bayonet base, which has an offset pin arrangement that physically prevents it from being seated in a socket designed for the BA15s base used by the 1156.
• Although the 1156 and PY21W share the same 12V, 21W single-filament rating, their differing base types mean they are not drop-in substitutes for one another, making trim-level identification necessary before rear turn signal replacement on 2017-2018 Optima vehicles.
• The rear turn signal bulb on the 2005-2007 Optima changed across that period. The 2005 model used the 1156NA, while the 2006-2007 models used the 2357, which is a dual-filament bulb with a different base contact configuration.
• All bulbs listed across both front and rear turn signal positions operate at 12V, consistent with standard 12-volt automotive electrical systems.