Audi S8 Back Up Light Bulb Size

Additional Notes

• The 7506 bulb type appears across the 2001-2003 Audi S8, making it the most frequently recurring bulb size in these specifications.
• The 921 is an ANSI-standardized wedge bulb classified under the T15 form factor, operating at 12V and 16W. It is specified for the 2007-2008 S8 backup light position.
• The T15 designation refers to a wedge-base bulb with a tubular envelope roughly 15 eighths of an inch wide. This base type does not use a separate socket pin, as the glass envelope itself forms the electrical contact.
• The 12177 and 12184 are Philips-assigned part numbers for halogen bulbs in specialty applications, both rated at 12V. They are specified for the 2013 and 2009 S8 models respectively.
• Because 12177 and 12184 are manufacturer-specific part numbers rather than ANSI industry codes, they do not carry the same cross-brand interchangeability that a standardized designation like 921 would imply.
• The 921 and the 12177/12184 bulbs all operate at 12V, which is consistent with standard automotive electrical systems. However, wattage and physical form factor differ across these types, meaning they are not interchangeable despite sharing the same voltage rating.
• The Audi S8 backup light specification changes across model years, with three distinct bulb types used at different points. Substituting a bulb from one model year into another is not supported by these specifications.