The Subaru GL brake light utilizes 1157, 1073, and P21W bulb sizes depending on the specific vehicle configuration. Available information covers the time range from 1975 to 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Subaru GL uses the 1157 bulb for brake lighting across the 1982-1989 model years, making it the most consistently specified bulb type in these brake light specifications.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output and a BAY15d bayonet base, which allows it to serve both brake and tail light functions within a single housing.
The BAY15d base on the 1157 is offset-pin, meaning the two pins sit at different heights to prevent incorrect installation of a single-filament bulb in a dual-filament socket.
The 1980-1981 Subaru GL brake lights use the 1073 bulb, a single-filament 12V, 13W unit with a BA15s bayonet base, which is not interchangeable with the dual-filament 1157 used in later model years.
The 1975 Subaru GL is specified with the P21W, an ECE-standard single-filament bulb rated at 12V and 21W with a BA15s base, reflecting a European-market or internationally sourced component rather than an ANSI-standard part.
Although the P21W and 1073 share the same BA15s base type, their wattage ratings differ at 21W and 13W respectively, and substituting one for the other would affect light output.
The 1156 bulb is specified for the Center High Mount Stop Light on the 1985-1989 Subaru GL, but only on vehicles equipped with Halogen Capsule Headlamps, indicating a conditional fitment tied to a specific trim or equipment package.
The 1156 operates at 12V and 21W with a BA15s base, and while it shares the same base type as the P21W, it is an ANSI-standard part rather than an ECE-standard one.
The 1156 and 1157 share the same 12V, 21W rating for their primary filament, but the 1157 adds a secondary 5W filament, meaning the two bulbs are not interchangeable despite their similar output on the brake circuit.
The shift from the 1073 in 1980-1981 to the 1157 in 1982 represents a change from a single-filament to a dual-filament brake bulb configuration for the Subaru GL.