Open the hood of your Oldsmobile and support it with the prop rod. Locate the access hole above the headlight; there is one above each headlight, allowing access to the bulbs.
Determine whether the high or low beam is not working. Changing either bulb uses the same process and they sit next to each other in the headlight assembly.
Reach into the access hole and turn the headlight bulb 1/4 turn, then pull the bulb straight back out of the retaining ring. There are three tabs on the bulb that must align with the slots on the retaining ring for the bulb to come out.
Disconnect the electrical connector from the base of the bulb after releasing the locking tab. Pull the connector straight off the bulb from the connector not the wires.
Connect a new bulb to the wiring harness connector, pressing the bulb and connector together until the locking tab engages. Install the new bulb into the back of the headlight housing then turn it to lock the bulb under the retaining ring.
Turn the headlights on to verify they are working. Cycle them through the high and low beam settings as well.The Oldsmobile Delta 88 headlight uses a 9006 halogen bulb in the low beam position and a 9005 in the high beam. The bulbs sit in a composite headlight assembly and the bulbs are changed from the back of the assembly. The process for changing them is the same whether it is a high beam or low beam bulb that his not working. Replacement bulbs for the high beam and low beam are available at most auto parts stores and through the dealership.