The Subaru RX brake light utilizes a 1157 bulb size for illumination across all listed vehicle applications. Data for the specified component covers the period from 1985 through 1989.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Subaru RX uses the 1157 bulb for its brake lights across the 1985-1989 model years.
The 1157 is a dual-filament bulb operating at 12V with a 21W/5W output, meaning its two filaments serve separate functions at different wattages within the same housing.
The 1157 uses a BAY15d bayonet base, which features two offset pins that prevent incorrect installation of a single-filament bulb in its place.
The center high mount stop light on the Subaru RX takes the 1156 bulb across the same 1985-1989 model years.
The 1156 is a single-filament bulb rated at 12V and 21W, using a BA15s bayonet base with a single locating pin.
The BA15s base of the 1156 and the BAY15d base of the 1157 are physically distinct, and the two bulb types are not interchangeable despite their similar appearance and shared 15mm base collar size.
Both the 1157 and 1156 are ANSI-standardized bulbs recognized across the United States and Canada, placing them within a widely distributed specification category.
The dual-filament design of the 1157 makes it suitable for positions requiring both a running light and a brake light signal from a single socket, which is consistent with its use in the main brake light position.
The 1156, being a single-filament bulb, is suited for dedicated stop light functions where no secondary running light output is required, as reflected in its placement in the center high mount stop light position.