The Audi V8 Quattro uses 12961 bulb size for front side markers and P21/5W bulb size for rear side markers. The replacement chart covers 1990 to 1994 vehicle production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Audi V8 Quattro uses two distinct bulb types across its front and rear side marker positions for the 1990-1994 model years.
The front side marker on the Audi V8 Quattro (1990-1994) takes the 12961 bulb, a miniature wedge-type T10 bulb rated at 12V and 5W with a W2.1x9.5d base.
The 12961 is a Philips part number designation for a T10 wedge bulb, meaning equivalent bulbs from other manufacturers must match the W2.1x9.5d base and 12V, 5W rating to be considered interchangeable.
The rear side marker position uses the P21/5W, a dual-filament bulb rated at 12V with a 21W primary filament and a 5W secondary filament, mounted on a BAY15d bayonet base.
The BAY15d base on the P21/5W features offset pins, which physically prevents incorrect single-filament substitutes with a BA15d base from seating in the socket, as the pin positions differ.
The P21/5W follows the ECE standard, a regulatory framework used across Europe and many international markets, indicating the bulb conforms to defined output and signalling performance requirements.
The front and rear side marker bulbs are not interchangeable with each other, as the T10 wedge base and the BAY15d bayonet base are mechanically incompatible socket types.
The wattage difference between the two bulb types is notable: the front 12961 operates at 5W, while the rear P21/5W carries filaments rated at 21W and 5W, reflecting different functional demands between the two positions.