Audi Q5 front fog light uses H11 bulb size while rear fog light requires 921 bulb size for replacement. The chart covers bulb size specifications across 2009 to 2019 production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Audi Q5 front fog light takes an H11 bulb across the 2009-2018 model years.
The H11 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PGJ19-2 base.
The H11 bulb is produced under the ECE standard, which governs automotive lighting regulations in Europe and much of the world, and it also carries approval for use in the United States.
The Audi Q5 rear fog light takes a 921 bulb across the 2015-2019 model years.
The 921 is a T15 wedge-type bulb rated at 12V and 16W, produced under the ANSI standard applicable in the United States and Canada.
The H11 and 921 bulbs are governed by different standards bodies and serve entirely different positions on the vehicle, making them non-interchangeable with one another.
The PGJ19-2 base of the H11 is a keyed, twist-lock connector, meaning only bulbs with that specific base configuration are physically compatible with the front fog light socket.
The T15 wedge construction of the 921 relies on the bulb's glass envelope and lead wires to make direct contact with the socket, requiring no separate base locking mechanism.
At 55W, the H11 front fog bulb draws considerably more power than the 16W rear fog bulb, reflecting the greater light output required for forward illumination in low-visibility conditions.