Oldsmobile Delta 88 Headlight Bulb Size

Additional Notes

• The Oldsmobile Delta 88 headlight specifications span three distinct bulb technologies across its model history. The 1965-1975 model years used sealed beam units in round and square form factors, the 1976-1986 model years transitioned to rectangular sealed beam units, and the 1987-1991 model years adopted the 9004 halogen bulb format.
• The 9004 bulb, used in the Delta 88 for both high and low beam functions from 1987-1991, is a dual-filament halogen type with a P29t base rated at 12V with 65W output on high beam and 45W on low beam. A single bulb unit serves both beam functions through its two filaments.
• Sealed beam units such as the H4651, H4652, H4656, H5001, and H5006 are not replaceable bulbs in the conventional sense. The entire lens, reflector, and filament assembly is replaced as one unit when the light fails or is damaged.
• The H5001 and H5006 sealed beam units used in the Delta 88 from 1965-1975 differ in physical form factor. The H5001 is a 4-inch square unit designated for high beam use, while the H5006 is a 5.75-inch round unit designated for low beam use. These two types are not interchangeable with each other.
• The 4x6-inch rectangular sealed beam format appears across multiple designations in the Delta 88 specifications. The H4651 serves the high beam position, while the H4652 and H4656 serve the low beam position across various years from 1976-1986. Despite sharing the same physical form factor, these designations reflect different beam pattern configurations and are not interchangeable across positions.
• The low beam specifications for the Delta 88 show variation within the 1976-1986 period. The H4656 was specified for low beam use in 1976, 1977, 1979, and 1982, while the H4652 was specified in 1978, 1980-1981, and 1983-1986. Both are 4x6-inch rectangular sealed beam units but carry distinct ANSI designations.
• All bulb and sealed beam types listed in the Delta 88 specifications conform to ANSI standards applicable in the United States and Canada, and all operate on a 12V electrical system regardless of type or era.
• The transition from sealed beam units to the 9004 halogen bulb in 1987 represents a shift from a system where the entire optical assembly is a consumable component to one where only the bulb itself requires replacement, leaving the headlight housing intact.