The Hino SG23 headlight assembly uses an H4651 bulb size for high beam and H4652 or H4656 bulb sizes for low beam applications. The replacement chart covers 1987 to 1992 production 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 H4651, H4652, and H4656 bulb types are all ANSI-standardized sealed beam units used across the Hino SG23 headlight system. ANSI standardization means these units conform to a fixed set of electrical and optical specifications recognized across the United States and Canada.
All three bulb types share a 4x6-inch rectangular sealed beam format. In this construction, the filament, reflector, and lens are fused into a single glass envelope, meaning the entire unit is replaced rather than an internal bulb element.
All sealed beam units specified for the Hino SG23 operate at 12 volts, which is consistent with standard automotive electrical systems of that period.
The H4651 is specified as the high beam headlight unit for the Hino SG23 across the full 1987-1992 model range without variation.
The low beam headlight specification for the Hino SG23 changed between model years. The H4656 was used in 1987-1988, while the H4652 replaced it from 1989-1992. These two units are not interchangeable despite sharing the same physical 4x6-inch sealed beam format, as each carries a distinct ANSI designation with differing optical output characteristics.
The H4652 is described as a variant of the H4651. Although both share the same physical format and voltage rating, they carry separate ANSI designations, reflecting differences in beam pattern or light output that make them application-specific rather than mutually substitutable.