To be certain, you should:
* Consult your owner's manual: This is the most reliable source.
* Look at a diagram: Online parts stores (like AutoZone, Advance Auto Parts, etc.) often have diagrams showing the location of components for your specific year and model. Enter your year, make, and model to find the diagram.
* Check online forums: Oldsmobile enthusiast forums might have pictures or discussions about this.
Looking near the power steering pump will drastically narrow your search. The reservoir is usually a plastic container with a cap and dipstick (or at least markings to show the fluid level).