Buick Opel front and rear turn signal bulbs both utilize a 1157 bulb size for proper operation. The replacement chart covers vehicle production spanning 1976 to 1979 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 1157 is the sole bulb type specified for the Buick Opel across all listed positions and model years, covering both the front and rear turn signals from 1976-1979.
The 1157 is an ANSI-standardized bulb, meaning its physical and electrical characteristics conform to a defined North American specification recognized in both the United States and Canada.
The 1157 operates on a 12-volt electrical system, which was the standard automotive voltage architecture in production vehicles of this era.
As a dual-filament bulb, the 1157 contains two separate tungsten filaments within a single glass envelope, allowing it to serve two distinct lighting functions from one unit.
The two filaments in the 1157 are rated at 21 watts and 5 watts respectively, where the higher-wattage filament typically handles the active turn signal flash and the lower-wattage filament handles a secondary function such as a parking or running light.
The 1157 uses a BAY15d bayonet base, a two-pin offset bayonet mount in which the two pins are positioned at different heights along the base, a design that prevents incorrect single-filament bulbs from being seated in the socket.
Because the BAY15d base is offset, substituting a single-filament BAY15s bulb, such as the 1156, is physically prevented by the socket geometry, making accidental filament mismatch unlikely.
The identical 1157 specification across both the front and rear turn signal positions means the Buick Opel uses the same bulb in all four turn signal sockets, with no positional variation in the 1976-1979 model years listed.