Saturn Aura front turn signal bulbs use 5702AK or 4157NA sizes, while rear turn signal bulbs use 3057 size. The replacement chart covers 2007 to 2009 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Saturn Aura uses T25 wedge-style dual-filament bulbs across all three turn signal positions covered in these specifications, meaning the front and rear sockets share the same physical bulb format.
All bulbs listed operate at 12 volts with a 27W/7W dual-filament rating, where the higher wattage filament serves the turn signal function and the lower wattage filament serves a secondary lighting function such as parking or running light duty.
The rear turn signal position on the Saturn Aura uses the 3057 bulb for all three model years covered, 2007-2009, making it the most consistently specified bulb across the entire dataset.
The 3057 is an ANSI-standardized bulb recognized in both the United States and Canada, which reflects its broad availability across the North American automotive market.
The front turn signal position alternates between two bulb sizes depending on model year. The 2007 and 2009 Aura take the 5702AK, while the 2008 model takes the 4157NA.
The 5702AK is a Sylvania-specific part number rather than an ANSI standard designation. It refers to a 3157-based bulb with an amber coating applied to a clear glass envelope to produce the amber light output required for turn signal use.
The 4157NA used in the 2008 front turn signal position achieves its amber output through natural amber-tinted glass rather than a coating, which is the distinction between it and the 5702AK despite both sharing the same T25 form factor and 12V/27W/7W electrical rating.
Because the 5702AK and 4157NA share identical physical and electrical specifications, the functional difference between them is limited to the method of amber light production, one using a coated bulb and the other using tinted glass.
The 3057 bulb, used at the rear, does not carry an amber designation in its standard specification, which contrasts with the amber-specific front turn signal bulbs listed for the same vehicle.
Substituting a non-amber bulb in a socket specified for an amber-coated or amber-glass variant would alter the color output of the turn signal, which is subject to vehicle lighting regulations in most jurisdictions.