1993 Buick Riviera Owner's Manual - Page 236

PowerSteering Fluid What to Add: Refer to the Maintenance Scheduledetermine what to kind of fluid to use. See "Recommended Fluids and Lubricants" in the Index. How To Check Power SteeringFluid: Unscrew the cap and wipe the dipstick with a clean rag. Replace the cap and completely tighten it. Then remove the cap again and lookat the fluid level on the dipstick. When the engine compartment is hot, the level should beat the "HOT" mark. When the engine compartment is cool, the level should beat the "FULL COLD" mark.