The Hino SG231 high beam headlight uses an H4651 bulb size, while low beam headlight applications require either H4656 or H4652 bulb sizes. The replacement chart covers vehicle production years spanning 1989 to 1992 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, H4656, and H4652 are all ANSI-standardized sealed beam units used in the US and Canadian markets. Each operates at 12V and follows the 4x6-inch rectangular sealed beam format, meaning the lens, reflector, and filament are fused into a single non-serviceable assembly. When the filament fails, the entire unit requires replacement rather than a bulb swap.
The Hino SG231 uses the H4651 sealed beam for the high beam headlight across all four model years covered, spanning 1989-1992. This consistency means the same sealed beam unit applies to the high beam position throughout the full range of listed years.
The low beam headlight position shows a fitment change on the Hino SG231 between 1991 and 1992. The H4652 is specified for 1989-1991, while the H4656 replaces it for the 1992 model year.
Although the H4652 is described as a variant of the H4651, the two are not listed as interchangeable within these specifications. The H4651 is assigned exclusively to the high beam position, and the H4652 is assigned exclusively to the low beam position for 1989-1991.
The H4656, used in the 1992 low beam position, is a distinct part number from the H4652 it replaced. Both share the same 4x6-inch rectangular sealed beam construction and 12V rating, but they carry separate ANSI designations, which typically indicates differences in light output, beam pattern, or filament configuration.
Because all three sealed beam types follow the ANSI 4x6-inch rectangular standard, physical housing size is consistent across the high and low beam positions. However, ANSI part numbers govern the correct optical and electrical specification for each position, and substituting one number for another is not supported by these specifications.