Oldsmobile Cutlass Calais Headlight Bulb Size

Additional Notes

• The Oldsmobile Cutlass Calais uses three distinct headlight technologies across its model years: sealed beam units in earlier years and a dual-filament halogen bulb in later years.
• The 9004 bulb, used in the 1988-1991 Cutlass Calais for both high and low beam functions, is a dual-filament halogen type with a P29t base rated at 12V and 65W on high beam and 45W on low beam. A single bulb handles both beam functions in one housing.
• The H4651 and H4652 sealed beam units, used from 1980-1984, are both 4x6-inch rectangular ANSI-standard units operating at 12V. The H4651 serves the high beam position while the H4652 serves the low beam position, meaning the two positions require different part numbers despite sharing the same physical size.
• The H6054 sealed beam unit, used in 1978-1979, is a 5x7-inch rectangular ANSI-standard unit rated at 12V. It serves both the high and low beam positions in those years, requiring only one part number for both functions.
• The H4656, used exclusively for the low beam position in 1980, is a 4x6-inch rectangular sealed beam unit. It differs from the H4652 used in 1981-1984 despite occupying the same position, so the two are not interchangeable.
• All sealed beam types, including the H4651, H4652, H4656, and H6054, are not bulb-replaceable units. The entire sealed assembly is replaced when the light fails, rather than an internal filament or capsule.
• The shift from sealed beam units to the 9004 halogen bulb between the 1984 and 1988 model years represents a change in the replacement method, from whole-unit sealed beams to a serviceable bulb within a retained housing.
• All bulb and sealed beam types specified for the Cutlass Calais conform to ANSI standards applicable in both the United States and Canada.