The Merkur XR4Ti uses a 168 bulb size for both front and rear side marker applications. The replacement chart covers 1985 to 1989 model years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Merkur XR4Ti uses the 168 bulb for both front and rear side markers across its entire 1985-1989 production run.
The 168 is an ANSI-standardized bulb recognized across the United States and Canada, operating at 12 volts and 4.9 watts.
The 168 follows the T10 form factor, a miniature wedge-base design that seats without a twist-lock mechanism, relying instead on socket tension to hold the bulb in place.
Because the front and rear side marker positions share the same 168 specification, a single bulb type serves all four side marker housings on the vehicle.
The T10 wedge base is a widely used standard, meaning the 168 is physically interchangeable with other T10-based bulbs, though wattage and lumen output may differ between variants.
At 4.9 watts, the 168 falls within the low-wattage range typical of marker and courtesy lighting, where heat output and current draw are kept minimal.