For a 1973 Cadillac Eldorado convertible top hydraulic system, you should use
automatic transmission fluid (ATF). Specifically, the type recommended in your owner's manual is ideal, but if you don't have that, a common ATF like Dexron II or III will generally work. However, always check your owner's manual first as there might be a specific recommendation.
Important Note: Never use power steering fluid or other types of hydraulic fluid in your convertible top system. Using the incorrect fluid can damage seals and other components.
