GMC 1998 Savana Van Owner's Manual page 266

What to Use
Adding Washer Fluid
To determine what kind of fluid to use, see
"Recommended Fluids and Lubricants" in the Index.
Always use the proper fluid. Failure to use the proper
fluid can cause leaks and damage hoses and seals.
Windshield Washer Fluid
What to Use
When you need windshield washer fluid, be sure to read
the manufacturer's instructions before use. If you will be
operating your vehicle in an area where the temperature
may fall below freezing, use a fluid that has sufficient
protection against freezing.
Open the cap labeled WASHER FLUID ONLY. Add
washer fluid until the tank is full.
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